Micromachines doi: 10.3390/mi17050629

Authors: Xiaoqing Xing Xinjie Fan Ruoshi Li Boxin Lu Yin Ma Chun Jia Dong Gao Jie Wu Guogang Ren Mian Zhong

With the rapid development of flexible electronics technology, flexible wearable sensors based on Lanthanum Strontium Manganese Oxide (La1-xSrxMnO3) have garnered extensive attention in recent years due to their excellent multi-functional integration, environmental stability and biocompatibility. This review systematically analyzes the preparation methods, process optimization strategies, multi-performance integration technologies, and the expansion of the application field of La1-xSrxMnO3-based flexible sensors. Firstly, the basic characteristics and sensing mechanism of the La1-xSrxMnO3 material were presented, including its temperature sensitivity, strain response characteristics, and magnetoresistance effect. Secondly, the fabrication process of flexible sensors was elaborately discussed, with a focus on analyzing crucial technologies, such as laser induction and transfer printing technology. Subsequently, the strategies for regulating the electrical, thermal, and mechanical properties of materials through element doping, along with the multimodal sensing integration and signal decoupling methods, were expounded. Furthermore, the actual performance of this type of sensor in fields such as health monitoring, human–computer interaction, and extreme environment applications was summarized. Finally, the challenges and future development directions of La1-xSrxMnO3-based flexible sensors are outlined, providing theoretical references for the design and optimization of next-generation flexible electronic devices.

Micromachines doi: 10.3390/mi17050628

Authors: Jinhuai Zhou Zhi Zhang Yao Yao Fei Wang Hanmin Wu Mengjie Shi Wenke Zhou

High-performance electromagnetic wave absorption materials are desperately needed due to the growing serious electromagnetic interference and pollution issues brought on by the quick growth of modern electronic technology and wireless communication. This work uses the organic–inorganic hybrid perovskite MAPbBrxI3−x as a model system to address the problem of restricted loss mechanisms and the challenges in changing the absorption bandwidth of single-component wave-absorbing materials. It achieves systematic tuning of electromagnetic wave absorption performance, especially within the effective working frequency spectrum, through accurate halogen site engineering. According to the study, MAPbI3 (MPI), MAPbBr1.5I1.5 (MPIB), and MAPbBr3 (MPB), which were synthesized using the anti-solvent approach, all demonstrated exceptional microwave absorption capability, with maximum reflection loss values exceeding −37 dB, among which MPB achieves a remarkable value of −42.41 dB at 16.60 GHz. More significantly, this work shows a distinct structure-property relationship between the effective absorption peak frequency range of this series of materials and their band structure: the strongest absorption peak shows a regular blue shift as the material bandgap widens and the bromine content rises. This finding suggests that focused tailoring of the operating frequency band in wave-absorbing materials can be achieved by manipulating the band structure of perovskites by varying the halogen concentration. In addition to confirming the significant application potential of organic–inorganic hybrid perovskites in the field of microwave absorption, this study offers a novel research perspective and material template for precisely and programmably controlling the absorption frequency band of wave-absorbing materials based on their basic electronic structures.

Micromachines doi: 10.3390/mi17050627

Authors: Hongfei Wang Zheng Li

A novel 3D detector with a semi-spherical electrode detector structure is proposed in this study. The semi-spherical electrode is formed by concentric deep circular-type trenches of varying depths. These concentric trenches can be simultaneously deep-etched using DRIE (Deep Reactive-Ion Etching) depths obtained from our calculations for a certain time at a given aspect ratio. The focus of this work is the conceptualization, design considerations, 3D modeling, and electrical simulation of the proposed 3D detector. The detector’s electrical properties, including electric potential distribution, electric field distribution, electron concentration distribution, full depletion voltage, leakage current, and capacitance, were simulated using a technology computer-aided design (TCAD) tool. Simulation and analysis of the detector’s performance post-irradiation were also conducted. The small capacitance of our semi-spherical electrode detector renders it highly suitable for applications in photon sciences (e.g., X-ray).

Micromachines doi: 10.3390/mi17050626

Authors: Wuhao Liu Maoxin Song Shuming Shi Mingchun Ling Hengwei Qin Hengrui Guan Jun Wang Jin Hong

Achieving high-precision overlay target center localization is critical for image-based overlay (IBO) metrology in advanced semiconductor manufacturing. This paper proposes a novel IBO target localization algorithm based on symmetry center matching. Leveraging the symmetry design of the IBO optical system as a physical prior, the algorithm reformulates center localization as a global correlation optimization problem. The grayscale projection profile of a single-sided edge is extracted, spatially mirrored, and used as a reference template for sliding correlation matching against the opposite edge. The symmetry center is then determined from the peak of the Pearson correlation coefficient curve. Simulation results demonstrate a center localization accuracy better than 0.00013 pixels (3σ), with repeatability precision remaining within 0.012 pixels (3σ) under stringent noise and blur conditions. Experimental validation yields object-space repeatability precision of 0.129 nm (3σ) and 0.144 nm (3σ) in the X and Y directions, respectively, surpassing the 0.32 nm measurement uncertainty requirement for advanced process nodes. The average single-frame processing time is approximately 0.07 s, demonstrating that the proposed algorithm simultaneously satisfies the demands of high precision and high throughput.

Micromachines doi: 10.3390/mi17050625

Authors: Cong Mei Tianze Zheng Ziyang Ding Dan Zhang Yuan Xu Huiyao Zhao Liu Chang Qiuhan Hu Chenhui Xia Shuli Liu Liyi Li

Polymer insulation layers such as polyimide (PI) have gradually replaced inorganic dielectric layers (SiO2, SiCN) in the integrated packaging process of hybrid bonding (HB). PI can fill the gaps in the thermal compression bonding process and help to obtain a good Cu/Polymer bonding interface. At present, the existing post-crack double cantilever beam tensile test (PBC-DCB) has been successfully applied to the quantitative measurement of bonding strength of hybrid bonding with inorganic materials, but this method only considers elastic behavior. Since PI exhibits viscidity, elasticity and plasticity, knowing how to correlate these properties to the bonding process is challenging. Whether PBC-DCB is suitable for the characterization of PI bonding is unclear. This paper presents a comprehensive experimental and finite element analysis (FEA) study on the PI–PI bonding interface. Firstly, nanoindentation experiments and simulations are performed on the prepared PI interface to obtain key elasticity and plasticity parameters. Then, the bonding strength is characterized by the PBC-DCB test. Theoretical and experimental results show that the plasticity of PI causes energy dissipation during stretching, resulting in a deviation of approximately 2.51% compared with pure elasticity. Based on experimental data, the Cohesive Zone Model (CZM) FEA method is used to simulate the crack propagation. The results indicate that the Embedded Process Zone (EPZ) model can accurately describe crack initiation and delamination behavior, with a margin of error of about 3.61%. Finally, based on the EPZ CZM, defects such as bonding void and wafer warpage are further discussed in relation to bonding strength measurement.

Micromachines doi: 10.3390/mi17050624

Authors: Yuanjun Shen Tianling Zhang

A single-band-notched ultra-wideband (UWB) low-sidelobe planar array antenna for millimeter-wave (mmWave) applications is presented. The antenna element employs a planar dipole excited through an H-shaped coupling slot to achieve broadband impedance matching, while a centrally loaded parasitic patch acts as a half-wavelength resonator to generate a controllable notch band. Additional parasitic patches are introduced to recover the high-frequency matching without degrading the notch response. An 8×8 array is then developed using a Taylor-weighted feed network implemented with three classes of 1-to-4 microstrip power dividers. Measured results show that the array operates from 19.0 to 45.0 GHz with VSWR<2, while providing a rejection band from 35.0 to 38.5 GHz. The notch suppresses the realized gain by about 5 dB around 37.0 GHz, the peak gain reaches 20.5 dBi in the passband, and average sidelobe levels better than −17 dB are obtained. The proposed design provides a practical approach for combining ultra-wide bandwidth, in-band interference rejection, and low-sidelobe radiation in a compact mmWave planar array.

Micromachines doi: 10.3390/mi17050623

Authors: Muniyandi Maruthupandi Nae Yoon Lee

Neurological disorders, diabetes, cancer, and infectious diseases remain major global health concerns, particularly in low- and middle-income countries with insufficient access to accurate and rapid diagnostics. Conventional biochip sensing platforms, while effective, are often constrained by complex instrumentation and have limited capability for handling complex and large datasets. This review aims to address these limitations by evaluating the integration of artificial intelligence (AI) with biochip technology improve biomedical diagnostics. We systematically analyze recent advances in AI-integrated biochips, such as spectroscopic, paper-based, lab-on-chip, and microfluidic platforms integrated with reinforcement learning, machine learning, and deep learning models. These pre-trained AI models simplify pattern recognition, feature extraction, and automated data processing from a variety of biosensor outputs, such as electrochemical, fluorescence, and colorimetric signals. The reviewed studies indicate improved real-time diagnostic sensitivity and accuracy across biomedical applications. Overall, we discuss ongoing challenges and future perspectives toward explainable, robust, and smartphone-assisted AI-integrated biochips for rapid and accurate diagnostics. The review offers a comprehensive overview of AI-integrated biochips to support effective disease detection and clinical decision-making.

Micromachines doi: 10.3390/mi17050622

Authors: Bobin Seo Sung-Min Park

This paper proposes an energy-efficient LiDAR receiver topology based on a time-to-voltage converter (TVC) followed by a 5-bit SAR ADC. By converting the time-interval between START and STOP signals into the voltage domain, the proposed topology avoids the complexity of conventional TDC-based designs and enables the use of a moderate-speed, energy-efficient SAR ADC. The proposed TVC in the proposed LiDAR receiver consists of an on-chip avalanche photodiode (APD), a CMOS transimpedance-limiting amplifier (CTLA), a time-gating circuit, a ramp generator, and a peak-and-hold (PDH) block. Thereafter, the converted voltages are digitized by a VCM-based single-ended SAR ADC with a binary-weighted CDAC, a strong-arm latch comparator, and custom digital logic. A reset generator is also incorporated to coordinate the sampling, comparison, and settling phases. The proposed LiDAR receiver is implemented in a 180 nm CMOS process, where the TVC occupies an area of 171 μm × 98.8 μm, while the TVC-SAR receiver occupies 417 μm × 356 μm, respectively. The proposed LiDAR receiver consumes 13 mW from a single 1.8 V supply, in which the SAR ADC consumes 3.68 mW only. The TVC-SAR receiver resolves the time-intervals ranging from 7 ns to 32.1 ns with a resolution of 0.81 ns. Hence, the proposed topology provides an energy-efficient solution along with its reduced circuit complexity and chip implementation for short-range LiDAR applications.

Micromachines doi: 10.3390/mi17050621

Authors: Xuyun Peng Shuang Fan Jingfeng Tai Jinqiu Zhang Xinhua Qiu Suliang Chen Weihua Li Yingmeng Zhang

Nonaqueous potassium-ion batteries (KIBs) are emerging as promising next-generation energy storage systems owing to their abundant resources and high energy density. However, their large-scale application is hindered by structural degradation and sluggish kinetics resulting from the large ionic radius of K ions. Engineering electrode materials with open frameworks, such as two-dimensional (2D) layered structures, present an effective strategy to address these challenges by providing rapid ion diffusion pathways and robust host structures. Herein, a rational interlayer engineering strategy is developed by intercalating phenylamine derivatives with varying molecular sizes (P-butylaniline: PTA, P-Methylaniline: PMA, and phenylamine: PA) into layered 2D VOPO4 nanosheets. The intercalation of PANI derivatives progressively expands the interlayer spacing from 0.76 nm (pristine VOPO4) to 1.58, 1.85, and 2.09 nm, while maintaining the structural integrity of the layered framework. Notably, the regulated interlayer expansion (from 0.76 to 2.09 nm) not only provides enlarged diffusion pathways for rapid K+ ion intercalation/deintercalation kinetics, but also facilitates the formation of oxygen vacancies that may serve as additional active sites for potassium storage. By correlating the electrochemical performance with the modulated interlayer distances, it is established that a preferred spacing of 1.85 nm achieves the best synergy between fast kinetics, high capacity, and structural stability. As expected, the electrode with the optimal interlayer spacing (1.85 nm) exhibits superior potassium-ion storage performance, delivering a high reversible capacity of 333.2 mAh g−1 at 0.1 A g−1 over 100 cycles and exceptional rate capability with 205.7 mAh g−1 retained at 1 A g−1, as well as maintaining remarkable stability up to 600 cycles even at high rates. This work innovatively proposes phenylamine derivative-enabled interlayer regulation as a promising approach for designing high-performance VOPO4-based electrode materials.

Micromachines doi: 10.3390/mi17050620

Authors: Jaewoo Jeong Sangwook Park

This study proposes a metasurface integrated reconfigurable unit-cell coupler designed for wireless power transfer (WPT) applications in unmanned aerial vehicles (UAVs). In near-field capacitive WPT systems, flexible UAV charging is restricted by rotational misalignment, which causes null power points (NPP) where energy transfer is suppressed. To address this, the proposed model emulates 1-bit digital coding states through Symmetric Excitation (SE) and Cross-Excitation (CE) states. Since precise unit-cell characterization is a prerequisite for array expansion, this research focuses on meta-atom-level analysis at 6.78 MHz with a deep sub-wavelength profile (0.002λ). Characterized through 3D full-wave analysis, the unit-cell achieves peak transmission coefficients of 0.945 for SE State and 0.903 for CE State. Crucially, these states exhibit complementary extinction angles at 90° and 45°, respectively, ensuring that the NPP of one state is effectively bypassed by the high transmissivity of the other. This dynamic switching between coding states maintains stable power transfer across a full 360° rotation, providing a technical foundation for scalable, intelligent metasurface-based wireless charging platforms.

Micromachines doi: 10.3390/mi17050619

Authors: Jun Zeng Rongguang Zhang Weicheng Ou Xuanzhi Zhang Shize Huang Xun Chen Guojie Xu

Nanofiber-based structures have shown considerable potential in semiconductor-related applications, including ultra-thin dielectric layers and flexible electronic devices, owing to their tunable micro-/nanoscale morphology. However, the manufacturing of these structures is often hindered by the complex multiparameter coupling and poor reproducibility inherent in conventional electrospinning processes. To address these challenges, this study develops an intelligent optimization framework for gas-assisted electrospinning by integrating Large Language Models (LLMs) with Bayesian Optimization (BO). A Gaussian Process Regression (GPR) surrogate model was established to navigate the high-dimensional parameter space efficiently. Comparative studies demonstrate that the proposed BO+LLM strategy not only outperforms pure data-driven BO and pure knowledge-driven LLM approaches but also surpasses the conventional Response Surface Methodology (RSM) baseline, successfully locating a verified minimum fiber diameter of 239 nm. Furthermore, through response-surface analysis, this work identifies a specific multiphysics collaborative window where electrostatic stretching and aerodynamic assistance are balanced. These findings provide a robust pathway for the reproducible fabrication of nanofiber-based electronic devices.

Micromachines doi: 10.3390/mi17050618

Authors: Qiufa Luo Gu Li Ningchang Wang Sirong Wang Jing Lu Congming Ke

Electrical discharge machining (EDM) is an efficient method for processing silicon carbide (SiC) substrates. However, the chemical modification mechanism of SiC substrates in the EDM process remains not fully elucidated. To clarify the material removal mechanism of SiC substrates in EDM, this study investigated the behaviors of SiC substrates under different discharge conditions through experimental analysis and interface temperature field simulation. Results indicate that the SiC substrates sequentially exhibit characteristic morphologies of surface oxidation, thermal decomposition, and fracture as discharge energy increases. A discolored layer composed of amorphous SiO2 is formed on the SiC surface in low-discharge energy. Crystalline silicon and graphitic carbon are generated from the thermal decomposition of SiC substrates in high-discharge energy. Excessively high discharge energy induces the breakdown of SiC substrates. A critical temperature threshold is identified that delineates the initiation of prominent thermal oxidation on the SiC surface. Temperature field simulations further reveal the correlation between EDM parameters and interfacial temperature variations, along with the mechanisms of material removal driven by thermal diffusion. This study deepens the fundamental understanding of the EDM removal mechanism of SiC substrates and is expected to provide a scientific basis for the efficient material removal of SiC substrates.

Micromachines doi: 10.3390/mi17050617

Authors: Yanbo Yuan Li Zhang Lei Li Mengyang Wang Wenjun Wang Lin Wang

In this study, La-doped TiO2-SiO2 composite films were deposited on glass substrates by radio-frequency magnetron sputtering. The evolution of microstructure and macroscopic properties was systematically investigated across an annealing temperature range of 350–650 °C. The results show that the La-doped TiO2-SiO2 composite structure effectively suppresses abnormal grain growth and delays the anatase-to-rutile phase transition, thereby improving the films’ high-temperature structural stability. Notably, the composite film annealed at 550 °C (LS-550) exhibits the highest anatase crystallinity and forms a dense, smooth (RMS = 1.37 nm), crack-free nanocrystalline network. In terms of wettability, the improved hydrophilicity is attributed to the combined effects of La incorporation and hydrophilic silanol (Si-OH) groups in the amorphous SiO2 phase. As a result, the water contact angle of the LS-550 film decreases dramatically to 28.0°, indicating excellent hydrophilicity. Moreover, the LS-550 film demonstrates an optimal photocatalytic degradation efficiency of approximately 76% for methylene blue, significantly outperforming the pure TiO2 film. Furthermore, the enhanced mechanical performance is associated with the combined effects of the SiO2-containing amorphous phase and the finer microstructure induced by La incorporation. Consequently, the critical load (Lc) of the LS-550 film reaches 75.64 mN, significantly exceeding that of the pure TiO2 film annealed at the same temperature (61.25 mN). In summary, the composite film annealed at 550 °C concurrently achieves high crystallographic thermal stability, robust interfacial mechanical durability, excellent surface hydrophilicity, and enhanced photocatalytic activity, thereby offering practical guidance for developing TiO2-based coatings with self-cleaning potential for high-rise building curtain walls.

Micromachines doi: 10.3390/mi17050616

Authors: Li Zhang Hai Wang Chunlai Yang Weiwei Duan Jingjing Peng

Under low wind speed conditions, conventional bluff body energy harvesters suffer from a single vibration mechanism and a narrow effective wind speed range, making it difficult to meet the continuous power supply demands of miniature electronic devices. In this paper, by systematically optimizing the number of triangular prisms N and the circumferential installation angle α, a parametrically adjustable star-shaped energy harvester (SEH) is proposed. The proposed structure consists of a cylindrical base with a tunable number of triangular prisms uniformly distributed along its circumference, aiming to reveal the regulation mechanism of the VIV-galloping coupling response and energy harvesting performance. Conceptual design and theoretical modeling of the SEH are first carried out. Then, three-dimensional fluid–structure interaction simulations are performed by varying N and α, and a prototype is fabricated for wind tunnel experimental validation. The results show that under the optimal parameter combination of N = 7 and α = 51.4°, the SEH achieves a maximum output voltage of 12.2 V at a wind speed of 3.41 m/s, with a maximum output power of 1.488 mW, and the effective wind speed range is broadened to 2.5~12.44 m/s. Compared with the conventional cylindrical energy harvester (CEH), the SEH (N = 7) increases the maximum output voltage by 44.38%, the maximum output power by 108.4%, and expands the effective wind speed range by 198.50%. Through systematic optimization of key geometric parameters, this study achieves synergistic regulation of flow-induced vibration modes and performance enhancement, providing a parametric design basis for efficient low-speed wind energy harvesting, which can promote the development of self-powered technologies for micro-sensors and IoT devices.

Micromachines doi: 10.3390/mi17050615

Authors: Gyuseong Chu Il-Ho Kim

Single-phase Cu4Bi4Se9 was successfully synthesized through a simple and rapid process combining mechanical alloying (MA) and hot pressing (HP). The phase formation behavior, microstructural evolution, charge transport characteristics, and thermoelectric properties were systematically investigated. X-ray diffraction analysis as a function of MA time confirmed that all powders crystallized into a single orthorhombic phase with space group Pnma. No decompositions or secondary phases were observed after HP sintering, indicating high phase stability. Thermogravimetric and differential scanning calorimetric analyses revealed distinct endothermic peaks at 714–717 K for all samples, corresponding to the onset of the decomposition of Cu4Bi4Se9. Microstructural observations showed that the relative density decreased with increasing HP temperature (>573 K), accompanied by grain growth and pore formation, reflecting the competition between Cu–Se interdiffusion and pore coarsening during high-temperature sintering. Hall effect measurements indicated p-type conduction for all samples, with carrier concentrations on the order of 1017 cm−3 and carrier mobilities of approximately 102 cm2 V−1 s−1. With increasing temperature, the electrical conductivity increased monotonically, while the Seebeck coefficient gradually decreased, resulting in a maximum power factor of 0.12 mW m−1 K−2 at 573 K. The total thermal conductivity remained extremely low, ranging from 0.33 to 0.48 W m−1 K−1, with the electronic contribution accounting for less than 10%, indicating that lattice thermal transport is dominant. The suppressed lattice thermal conductivity is attributed to the combined effects of Cu atomic rattling, asymmetric bonding induced by Bi 6s2 lone-pair electrons, and strong anharmonic phonon scattering arising from the complex crystal structure. Consequently, Cu4Bi4Se9 achieved a peak dimensionless figure of merit ZT of 0.19 in the temperature range of 573–623 K, demonstrating that the MA–HP process enables stable phase formation and competitive thermoelectric performance without post-annealing.

Micromachines doi: 10.3390/mi17050614

Authors: Yang Huang Bofeng Li Zhongyi Yu Xianruo Du Ruixin Chen Xiang Wang Jiaxin Jiang Gaofeng Zheng Huatan Chen

Metal nanoparticles are widely used in fibrous membrane materials due to their excellent antibacterial properties. However, metal nanoparticle-loaded fibrous membranes often face the trade-off between antibacterial performance and filtration efficiency. To address this issue, silver nanoparticle-loaded dendritic fibrous membranes were prepared via electrospinning technology in this study, and the dual optimization of antibacterial and filtration performance was achieved by adjusting the silver loading amount and fiber morphology. The results showed that the prepared silver nanoparticle-loaded PVDF dendritic fibrous membrane exhibited an outstanding air filtration performance with a filtration efficiency of 99.87% for 0.3 µm particulate matter, a pressure drop of 87.4 Pa, and a quality factor (QF) of 0.076 Pa−1. In addition, the membrane presented excellent antibacterial activity with inhibition rates of 99.9% and 99.8% against Escherichia coli and Staphylococcus aureus, respectively. This study provides a new insight into resolving the trade-off between air filtration and antibacterial performance of metal nanoparticle-loaded fibrous membranes and offers an important reference for applications in related fields.

Micromachines doi: 10.3390/mi17050613

Authors: Yin Shang Fengqin Li Chunhong Yang

This study investigates the time-periodic electroosmotic flow and solute transport of Maxwell fluid in a parallel microchannel with modulated surface charges. The Poisson–Boltzmann equation and the linearized momentum equations are solved using a superposition-based analytical approach. The influences of oscillation intensity, fluid elasticity, and electrokinetic parameters on the velocity and concentration distributions are examined. The results show that wall-potential modulation combined with a time-periodic electric field generates recirculating motion and oscillatory velocity patterns. Moderate oscillation strengthens both flow and solute transport, whereas stronger oscillation weakens transport efficiency. This work provides a quantitative analysis the interplay between oscillatory electroosmotic flow and solute transport in Maxwell fluid and clarifies the role of oscillation strength in controlling solute dispersion.

Micromachines doi: 10.3390/mi17050612

Authors: Yinglei Zhang Bo Yang Xiang Zou

Cancer continues to present a profound challenge due to high mortality and the inherent limitations of conventional treatments, including suboptimal targeting, systemic toxicity, and difficulty in overcoming physiological barriers. Micro/nanorobots (MNRs) offer a promising enhanced precision and efficacy in cancer therapy. This review systematically analyzes recent advancements in MNR applications, establishing a consistent framework that interlinks their diverse material compositions, propulsion strategies, and therapeutic functions. We critically compare various materials (inorganic, organic/polymeric, and biological/hybrid materials), elucidating their respective trade-offs in biocompatibility, biodegradability, and stimulus responsiveness. This paper further examines both internal (chemical and biological) and external (magnetic, light, and ultrasound) propulsion mechanisms, highlighting their strengths in overcoming biological barriers and enabling complex in vivo navigation, while also discussing their inherent limitations in control, fuel dependency, and tissue penetration. We then synthesize the therapeutic capabilities of MNRs across targeted drug delivery, phototherapy, radiotherapy, and immunotherapy, emphasizing common advantages like enhanced tumor specificity and reduced systemic side effects. A forward-looking perspective was also provided on the remaining challenges, particularly focusing on in vivo controllability, long-term biosafety, manufacturing scalability, and the significant hurdles in clinical translation. By offering a more critical and integrated analysis, this review underscores the immense potential of MNRs to revolutionize personalized precision cancer treatment, while candidly addressing the complex obstacles that must be surmounted for their successful clinical adoption.

Micromachines doi: 10.3390/mi17050610

Authors: Xiaoyu Li Weibin Rong Lefeng Wang Hongda Jia Xianghe Meng Hui Xie

Oral administration is an ideal route for colon-targeted drug delivery; however, precise delivery to the colon remains a challenge. This work presents a magnetically actuated millirobot combined with a traditional pH-dependent strategy. It aims to combine the advantages of the two methods: under normal physiological conditions, it enables autonomous targeted drug delivery, effectively reducing manipulation costs; in abnormal physiological environments, precise targeted delivery can be achieved via external magnetic intervention. The millirobot uses a magnetic composite shell and a pH-dependent film to encapsulate drug carriers. The pH-dependent film ensures an appropriate delay in drug release under different simulated pH conditions. The magnetic composite shell exhibits satisfactory magnetic responsiveness and can perform stable tumbling motion on the surface of the ex vivo intestinal tract, demonstrating good controllability and motility. Furthermore, the millirobot can carry different types of drug carriers to achieve tunable drug-release rates, thereby improving its versatility. These experimental results demonstrate that this pH-dependent magnetically actuated millirobot is a promising platform for reducing manipulation costs and enhancing the reliability of colon-targeted drug delivery.

Micromachines doi: 10.3390/mi17050611

Authors: Qinghua Wu Yan Gong Xiang Liu

High-density microelectrode arrays (HDMEAs) have become increasingly important tools in neuroscience and biomedical engineering because of their high spatial and temporal resolution for recording and modulating electrical activity across diverse biological systems. Initially developed for in vitro studies of cultured cells, HDMEAs are now being applied to increasingly complex models, including organoids, animal systems, and even human neural systems. These advancements enable a deeper investigation of cellular interactions, network dynamics, and disease mechanisms, as well as providing novel therapeutic and diagnostic tools for neurological disorders. This review explores the evolution of HDMEAs, emphasizing recent innovations in their design, fabrication, and functionalization. We discuss their applications across cellular models, organoid systems, animal studies, and human electrophysiology, and highlight current challenges such as biocompatibility, long-term stability, scalability, and translational deployment. Finally, we outline future directions for advancing HDMEA technologies in both research and clinical settings.

Micromachines doi: 10.3390/mi17050609

Authors: Qasem Ramadan Rana Hazaymeh Mohamed Zourob

We present a modular microfluidic platform for constructing miniaturized, compartmentalized cell culture systems that support monoculture, co-culture, and organ-on-a-chip models of human tissues. The devices provide architecturally defined three-dimensional microenvironments in which heterogeneous cell populations can be cultured in close proximity while maintaining precise spatial organization and independent access to each compartment. In vivo-like perfusion into, from, and between adjacent chambers is achieved via micro-engineered porous barriers that act as perfusion microchannels, enabling controlled convective and diffusive transport and recapitulating paracrine signaling between tissue units. As a proof of concept, we implement an adipose–immune co-culture model that reproduces key features of inflamed, insulin-resistant adipose tissue, including altered cytokine secretion and glucose uptake. Together, these features establish a versatile platform for the biofabrication of customizable single-organ and multi-organ in vitro models that more faithfully recapitulate human tissue structure and function for applications in disease modeling, immunometabolic studies, and preclinical drug testing.

Micromachines doi: 10.3390/mi17050608

Authors: Ehsan Kiani Harchegani Joško Valentinčič

The development of robotic systems that can operate safely and adaptively alongside humans requires actuators that combine compliance with reliable performance. Soft pneumatic rotary actuators (SPRAs) have emerged as promising candidates due to their inherent compliance, lightweight design, and capability to generate smooth rotational motion through elastic deformation. However, the diverse designs and performance characteristics of SPRAs make it challenging to identify optimal configurations for specific applications. This review comprehensively surveys current SPRAs, focusing on structural designs, materials, and fabrication methods. While SPRAs offer advantages such as reduced risk of injury and enhanced adaptability, significant challenges remain in optimizing torque output, rotational range, and durability. By comparing existing designs and highlighting open research challenges, this paper aims to guide the advancement of SPRAs, facilitating their integration into safe, effective robotic systems for industrial, medical, and wearable applications.

Micromachines doi: 10.3390/mi17050607

Authors: Siyi Zhang Shuhan Zhang Qian Fan Xianfeng Ni Xing Gu

GaN-on-Si light-emitting devices have been widely studied in the field of opto-electronics, while their optical performance and characterization accessibility are severely limited by the strong visible light absorption of the native silicon substrate. Conventional substrate transfer technologies often suffer from inherent thermal, optical, or mechanical bottlenecks. In this study, we developed a robust wafer-level substrate transfer strategy for 8-inch green GaN-on-Si light-emitting device wafers, utilizing a hybrid planarization process combined with SiO2–SiO2 direct bonding. The hybrid planarization precisely eliminated the 900 nm macroscopic steps, achieving sub-nanometer surface roughness for high-yield wafer bonding. We systematically investigated the physical evolution during substrate removal. Results indicate that the removal of the thick native silicon and high-stress buffer layers effectively released the additional in-plane biaxial compressive stress within the multiple quantum wells (MQWs), thereby mitigating the quantum-confined Stark effect (QCSE). Benefiting from the elimination of the light-absorbing silicon substrate and the incorporation of a built-in back-surface reflector (BSR), the transferred devices achieved a remarkable 1.9-fold enhancement in relative optical performance, albeit with an inherent trade-off of increased reverse leakage current while preserving basic diode functionality. Furthermore, optothermal dynamic analysis at high injection levels suggests a potential localized thermal bottleneck at the thick SiO2 bonding interface, where a hypothesized heat-induced spectral red shift may counteract the carrier-screening blue shift. This work provides a feasible wafer-level substrate transfer process for GaN-on-Si devices and offers systematic experimental insights into stress relaxation and optothermal behaviors during the substrate transfer process.

Micromachines doi: 10.3390/mi17050606

Authors: Xun Chen Weiming Shu Rongguang Zhang Shize Huang Xuanzhi Zhang

Coaxial electrospinning technology enables the fabrication of nanofibers with a core-shell structure, thereby facilitating the encapsulation of functional materials. Its efficacy lies in the precise regulation of mass transfer behavior at the sensing interface. However, achieving the controllable preparation of core-shell fiber structures in complex environments and quantitatively predicting their mass transfer kinetics remain challenging. This study aims to establish a predictive framework combining simulation and experiment. Firstly, finite element simulations using COMSOL clarified that increasing the shell thickness or decreasing its effective diffusion coefficient can significantly delay analyte transport. A model incorporating time-varying parameters further revealed the influence of polymer swelling on the initial release kinetics. Using the diffusion of an aqueous KCl solution as a model system, experiments confirmed that increasing the shell solution concentration is an effective processing strategy for enhancing the mass transfer barrier. Based on the Box-Behnken design and response surface methodology (RSM), a quantitative model linking key process parameters to release kinetic parameters was established. Model diagnostics indicated that the regression equation is significant and reliable. Validation experiments demonstrated that the model possesses good predictive capability for the key release kinetic parameters, with prediction errors within an acceptable range. The framework established in this study indicates that active design of the mass transfer behavior of core-shell fibers can be achieved through process control, providing a quantitative predictive tool and methodological reference for the preparation of controllable mass transfer interfaces for sensing applications.

Micromachines doi: 10.3390/mi17050605

Authors: Yuanjun Shen Xuli Feng Tianling Zhang

A wideband linearly polarized over-2-bit transmitarray antenna (TA) using the receiving-transmitting (R-T) scheme in the millimeter-wave band is presented in this work. The TA unit consists of two rectangular patches with a pair of bent branches, and the patches are connected by a metalized via. Two methods are used in this TA to obtain an over-2-bit phase shift of 0–90° and 180–270° from 18 GHz to 30 GHz. Firstly, 180° phase resolution is obtained by rotating the receiving patch around via by 180°. Secondly, by tuning the connection position between the branches and rectangular patch of the TA unit cell, a continuous 90° phase shift is further achieved. A TA prototype with 20×20 units is designed, fabricated, and measured. The measured 1 dB and 3 dB gain bandwidth is 24.9% (24.47–31.43 GHz) and 46.96% (20.45–33 GHz) respectively, with a peak gain of 25.17 dBi and a peak aperture efficiency of 55.2%. The measured results agree well with the simulated ones.

Micromachines doi: 10.3390/mi17050604

Authors: Wonchul Do Jeongmin Ju Minjin Kim Insoo Choi Sanghyun Jin Minkeon Lee Hyeonho Yang Jinho Jeong

This paper presents the electromigration (EM) performance of an embedded trace redistribution layer (ETR) in which the Cu trace features a rounded-bottom cross-sectional geometry and is encapsulated by a Ti barrier layer except for the top surface, with an optional top-side Ti cap. The ETR (with and without top-side Ti capping) and the conventional semi-additive-process (SAP) redistribution layer (RDL) are comparatively evaluated in terms of EM reliability. The ETR demonstrates a marked lifetime improvement compared with the SAP RDL. Notably, the Ti-capped ETR exhibits a minimal resistance increase in less than 10% even after a test duration of 4000 h. We discuss the key contributing factors and underlying mechanisms that support these improvements. Transmission electron microscopy (TEM) combined with atomic-percentage mapping confirms the effectiveness of Ti capping as a Cu diffusion barrier, showing continuous Ti coverage and no observable Cu diffusion. Electro-thermal simulations co-locate predicted thermal hot spots with experimentally observed open-failure sites, highlighting temperature-driven EM acceleration and the necessity of a barrier to suppress Cu–polymer interfacial oxidation. Stress simulations, together with EM failure analysis, indicate that the rounded-bottom Cu geometry alleviates local stress concentration and stress gradients, thereby creating conditions favorable for enhanced EM resistance.

Micromachines doi: 10.3390/mi17050600

Authors: Hoai Nguyen A. K. M. Fazlul Karim Rasel Mark A. Hayes

Opportunities abound in microfluidic technologies to impact how we understand extremely complex systems with many constituents which change with time and space. In these technologies, separation science plays a central role towards understanding everything from biology and healthcare to environmental monitoring to the search for life in the Solar system. Separations can amplify the capabilities of detection modalities by isolating targets and/or increasing their concentration while removing background constituents which can interfere with their sensing. In essence, separations increase the amount of information that can be gathered from a sample. The ideal features of next-generation separations capability are present in gradient insulator-based dielectrophoresis (g-iDEP), enabled by the length scale and precision of microfluidics. It acts through electric field interactions with particles, which enables unbiased (label-free) separations since all relevant particles, from atoms to cells, have an accessible response to electricity—either through linear (electrophoresis) or higher-order gradient (dielectrophoresis and related) effects. The technique isolates and concentrates, enabling improved detection function and multidimensional separations. Its foundational theoretical capabilities give it separations power on the order of 1:108, beyond the resolving power of the best mass spectrometers and ultra-high resolution spectroscopies. Experimental evidence is amassing that shows it to be a powerful tool that can resolve tiny differences in cells (antibiotic resistance versus susceptible in unlabeled paired isolates across many species) and differentiate single-point mutations in proteins. Its capabilities are still emerging, and this work aims to quantify the current practice and connect those approaches to the ultimate capabilities of the technique towards quantifying the dynamic range and resolving power of the strategy as a whole. The technique uses two methods of quantifying the electrophysical properties of the target, voltage sweep and spatial methods. The voltage sweep method is lower-resolution and serves as a search mode, while the spatial method is higher-resolution and quantifies the properties over a smaller defined range determined via the sweep method. These quantification methods are examined by collating existing experimental data, performing relevant Monte Carlo simulations, and finite element model calculations. These are summarized to understand the mechanisms currently limiting the technique, facilitate quantitative comparisons with traditional separation science capabilities in terms of resolution and dynamic range, and compare them to the theoretical limits of the strategy.

Micromachines doi: 10.3390/mi17050603

Authors: Kai-Wei Huang Chun Hao Wang Chien-Yin Lin Rajan Deepan Chakravarthy Hsin-Yu Liu Yu-Hsu Chen Mei-Yu Yeh Hsin-Chieh Lin

Conductive hydrogels are functional materials that combine soft, highly hydrated properties with electrical signal transmission capabilities. Their conductivity arises from ionic or electronic pathways, and the key design challenge is achieving good conductivity and long-term stability without compromising mechanical performance and biocompatibility. Among various conductive components, conductive polymers have attracted considerable attention due to their tunable mechanical properties, high electrical conductivity, good biocompatibility, and facile synthesis routes. In this study, a series of conductive hydrogels were rationally designed and fabricated by copolymerizing acrylamide and N,N′-methylenebisacrylamide with functionalized poly(vinyl alcohol) (PVA) and poly(3,4-ethylenedioxythiophene-co-thiophene) [P(EDOT-co-Th)]. The functionalized PVA provided multiple dynamic hydrogen-bonding sites, significantly enhancing the toughness of the hydrogel and its adhesion to various substrates, while the P(EDOT-co-Th) copolymer imparted good and stable electrical conductivity. By systematically adjusting the amount of functionalized PVA, the mechanical strength, adhesiveness, and durability of the conductive hydrogels were effectively optimized. The optimized hydrogel exhibited robust adhesion to a wide range of surfaces, excellent fatigue resistance, and long-term stability under repeated mechanical deformation. Moreover, the combination of mechanical resilience and good conductivity enabled precise and reliable signal transduction, highlighting its strong potential as a next-generation material for wearable strain and pressure sensors.

Micromachines doi: 10.3390/mi17050602

Authors: Youyuan Yue Liming Che Cancan Li Guangyin Lei

With the growing need for high-power density, high-efficiency power electronics, wide band gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), have been widely used in recent years. With high switching speed, stray inductance induced by packaging would cause voltage overshooting and oscillation during the switching transient, which should be mitigated at all costs. In this paper, a power module design based on a multilayer insulated metal substrate (MIMS) structure was proposed to effectively address the stray inductance concern based on the mutual-inductance cancelling effect. Fabrication process flow with high feasibility was also designed. Electrical and thermal simulations were conducted based on a power module with a nominal rating of 1200 V and 500 A. Compared to the planar module, the proposed design possessed much lower stray inductance (3.47 nH vs. 14.85 nH). In the transient thermal simulation, the proposed module exhibited a time constant 141.7% higher than that of the hybrid module with a ceramic substrate on the bottom but MIMS on the top, making it suitable for applications with high-constant power output requirements.

Micromachines doi: 10.3390/mi17050601

Authors: Siyi Chen Wanlu Hu Song Xue Qiongfang Zhang Jinyang Mu Shaoyi Liu Wenzhi Wu Dongchao Diwu Congsi Wang

The rapid advancement of high-performance computing has spurred growing demand for miniaturized, high-density, high-power, and highly reliable electronic packaging. Through-silicon via (TSV), as a pivotal technology enabling high-density integrated packaging, achieves vertical interconnection that reduces signal latency and power consumption while substantially improving system integration. However, inherent challenges persist due to coefficient of thermal expansion mismatches among heterogeneous materials in TSV and parasitic effects introduced by high-density TSV arrays, leading to critical concerns regarding thermomechanical reliability and signal integrity. This study focuses on TSV structures, investigating their thermomechanical reliability and electrical performance. First, the macro–micro model of 2.5D package structure was established to address cross-scale challenges based on Representative Volume Element (RVE) homogenization and sub-model technique. Then, an equivalent circuit model integrating transmission line network theory was developed and validated through full-wave electromagnetic simulations using S-parameter analysis to analyze signal transmission characteristics. Finally, by introducing an improved multi-objective grasshopper algorithm, the structural parameters of TSV are co-optimized using a genetic algorithm back propagation network (GA-BP) and an improved multi-objective grasshopper algorithm (IMOGOA) to enhance both thermomechanical reliability and electrical characteristics simultaneously. The proposed approach offers a practical and effective solution for improving the reliability and performance of high-density integrated packaging, providing valuable insights for future packaging design and optimization.

Micromachines doi: 10.3390/mi17050599

Authors: Xu Han Fangzhou Zhang Ruirui Chen Weixin Wang Yongjie Yu Zaijiong Yi Jingyi Yang Bo Liu Shilun Feng Jun Li Youzhi Feng

Soil eco-enzymes (i.e., microbial extracellular enzymes) play essential roles in terrestrial nutrient cycling and support ecosystem services. In this regard, their activities serve as indicators of soil health. However, conventional spectrophotometric and microplate fluorometric assays are often limited by lengthy reaction procedures, relatively high reagent consumption, and insufficient compatibility with complex soil matrices. In this investigation, we developed a portable, centrifugally driven microfluidic chip for the rapid and sensitive determination of multiple soil extracellular enzyme activities. This integrated platform automated sample aliquoting, reagent metering, mixing, and sedimentation, enabling the parallel measurement of eight enzymes. Such system demonstrated precise liquid control via capillary valves and high optical uniformity (<5% fluorescence variation). 4-methylumbelliferone (MUF)-based calibration exhibited strong linearity (R2 > 0.99) across diverse soil types. Compared with conventional microplate assays, the microfluidic method improved reproducibility (CV < 15%), enhanced the detection of weak fluorescence signals, and increased throughput while reducing reagent consumption. This field-ready platform provides a robust solution for standardized soil enzyme assessment and offers future potential for integration with AI-driven data analytics and large-scale ecological monitoring frameworks.

Micromachines doi: 10.3390/mi17050598

Authors: Zeenat Akhter Rehmat Iqbal Giedrius Janusas Sigita Urbaite Arvydas Palevicius

This paper presents a Micro-Electro-Mechanical Systems digital micromirror device (MEMS-DMD)-enabled ghost imaging (GI) framework for high-resolution imaging under scattering conditions. Unlike conventional ghost imaging systems that rely on fixed illumination patterns, the proposed approach exploits the high-speed programmability of a DMD to implement adaptive illumination strategies, enabling dynamic selection of informative patterns during data acquisition. This hardware-enabled pattern selection strategy improves sampling efficiency and reconstruction stability under the modeled fog conditions considered here. A hybrid convolutional neural network–generative adversarial network (CNN–GAN) model is employed as an inversion tool to reconstruct high-quality images from compressed bucket measurements. The proposed system achieves substantial improvements in reconstruction quality, with 23–40% gains in PSNR and 18–26% in SSIM compared to traditional ghost imaging methods, while reducing the number of required measurements by up to 60%. Additional performance gains are achieved through adaptive pattern selection enabled by the MEMS-DMD. The results demonstrate that integrating programmable MEMS hardware with learning-based reconstruction provides an effective solution for imaging under scattering conditions, with potential applications in remote sensing, environmental monitoring, and surveillance.

Micromachines doi: 10.3390/mi17050597

Authors: Zexin Ji Xiaowei Zhang Zhanbo Chen Shanshan Wang Wenbo Zhang Hao Ye Xiangyu Li

With the growing security requirements of sensor nodes in Internet of Things (IoT) systems, conventional silicon-circuit-based physical unclonable functions (PUFs) still face limitations in circuit overhead, design complexity, and system integration. To address these challenges, this paper proposes a lightweight gas sensor PUF (GS-PUF) design based on a Ni-doped SnO2 nanoscale gas sensor array. The proposed method exploits both the unavoidable process randomness introduced during sensor fabrication and the device-to-device electrical response variations induced by gas–material interactions as entropy sources, thereby enabling high-quality PUF response generation. At the device level, Ni-SnO2 nanomaterials are prepared by electrostatic spray deposition (ESD), and an indirectly heated gas sensor array is constructed to enhance the sensitivity and stability of the sensing response. At the algorithmic level, a random resistance balancing algorithm based on multi-sensor combinational comparison is proposed. By randomly comparing the summed resistances of multiple sensor clusters, a 128-bit multi-bit PUF response is generated, while the uniformity and independence of the output bits are effectively improved. Experimental results demonstrate that the proposed GS-PUF exhibits excellent randomness, uniqueness, and reliability: the information entropy of the PUF responses is greater than 0.99, approaching the ideal value; the probabilities of output bits “1” and “0” are 0.4988 and 0.5012, respectively, indicating a well-balanced distribution; the inter-device uniqueness reaches 49.8%, close to the ideal value of 50%; all items in the NIST randomness test suite are passed, with all p-values exceeding 0.01 and the minimum p-value being 0.0368, confirming a high level of statistical randomness confidence. In addition, long-term measurements under fixed laboratory conditions show that the PUF response reliability remains above 96%. Compared with other sensor-based PUFs, the proposed method provides a lightweight sensing-security integration approach for IoT sensor nodes by reusing intrinsic gas-sensor response variations and avoiding an additional dedicated silicon PUF circuit.

Micromachines doi: 10.3390/mi17050596

Authors: Zhiwei Yang Rui Ma Chuangye Yao Jinsong Song Jingrun Li Guangxu Cui Haiming Li Yuanxun Cao Dayong Ma

Nanoimprint lithography (NIL) is highly dependent on imprinted film as a pattern-transfer medium. This paper systematically reviews the research progress of imprint film materials for NIL. Firstly, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polyvinyl alcohol (PVA) and other single-polymer films are discussed, and their respective advantages (such as low surface energy, high optical transparency, water solubility) and inherent limitations (elastic deformation, demolding difficulties, humidity sensitivity)) are summarized. In order to overcome the above contradiction, researchers developed a composite imprint film structure, including an elastomer–rigid bilayer template and sandwich structure film, which achieved high resolution, conformal contact and facile demolding characteristics through mechanical function decoupling. At the same time, the emerging polymer/transparent electrode composite system (such as AgNWs/PVA, AgNWs/PDMS) gives the film active functions such as self-heating and antistatic ones, which effectively solves the key challenges in thermal management and electrostatic control. This paper comprehensively presents the evolution path from single-material to multi-functional composites, and provides guidance for the design of advanced imprint film for high precision, high reliability and large-scale NIL applications.

Micromachines doi: 10.3390/mi17050595

Authors: Wenhai Lu Chunyu Zhou Danying Wang Yong Liu Peiyi Wang Guanyu Wang

This work presents the design of a β-Ga2O3 MOSFET incorporating a P-type Ga2O3 buffer layer on a high-thermal-conductivity AlN/SiC composite substrate. The electrical characteristics of the device were simulated using Sentaurus TCAD. Results demonstrate that the integration of the composite substrate effectively mitigates self-heating effects, reducing the peak temperature (Tmax) from 776.5 K to 570.9 K at 300 K, while simultaneously increasing the threshold voltage (Vth) from −0.35 V to 1.52 V. Through systematic optimization of the P-Ga2O3 buffer layer thickness and doping concentration, the device achieves a breakdown voltage (Vbr) of 4781 V, a power figure of merit (PFOM) of 2.18 GW/cm2, an IDS, on/off ratio of 9.20 × 109, and cut-off/maximum oscillation frequencies (ft/fmax) of 1.29 GHz and 1.40 GHz, respectively. These findings provide a theoretical foundation for developing β-Ga2O3-based power devices with high breakdown voltage, improved thermal conductivity, and low specific on-resistance (Ron,sp).

Micromachines doi: 10.3390/mi17050594

Authors: Xiaomin Luo Zhiyun Du

Oxyresveratrol (Oxy) exhibits a diverse range of biological activities. However, its practical application is constrained by low aqueous solubility and chemical instability. In this work, Oxy-loaded zein (Z) nanoparticles (NPs) stabilized by a sodium alginate (Alg) coating (Oxy-Z/Alg NPs) were fabricated using an antisolvent precipitation method. The absence of crystalline peaks in X-ray diffraction analysis suggested that Oxy was dispersed as an amorphous phase in NPs, while the Fourier transform infrared spectra identified strong interfacial associations between the components. The stabilization of the NPs is attributed to the site-specific binding of Oxy with Z’s SER-162 and GLN-174 residues. Molecular docking, molecular dynamics simulations, and differential scanning calorimetry profiles evidenced the formation of intermolecular hydrogen bonds. Dynamic light scattering analysis showed that the nanocomplexes had a nano-scale dimension (243 ± 6 nm) and a zeta potential of −36 mV. SEM micrographs revealed that the NPs possessed a spherical morphology. The NPs exhibited colloidal stability against prolonged heating (80 °C for 75 min), ionic strengths (up to 100 mM NaCl), and pH range (2.0–10.0). Encapsulation within the Alg coating enhanced Oxy’s antioxidant capacity over its unprotected form by shielding its core bioactivity from degradation. The Oxy-Z/Alg nano-system shows significant promise for the encapsulation of Oxy, providing a practical basis for its integration into nutraceuticals and functional food fields.

Micromachines doi: 10.3390/mi17050593

Authors: Hui Geon Kong Yeon Woo Cha Sang Hyuk Lee Injun Song Yoomin Ahn

A textile-based membraneless microfluidic microalgae–microbial solar cell (μmMSC) was developed for low-cost, flexible, and sustainable power generation. Unlike conventional systems, the proposed device utilizes a textile substrate, enabling mechanical flexibility and simplified fabrication. Microfluidic channels were patterned via screen printing using hydrophobic Ecoflex, and conductive electrodes were fabricated using PEDOT:PSS combined with Ag2O and carbon nanotubes (MWCNT/SWCNT). At the anode, Synechocystis sp., Bacillus subtilis, and Shewanella oneidensis MR-1 were vertically co-cultured to enhance synergistic bioelectrochemical activity, while Scenedesmus obliquus was employed as a microalgae-based biocathode. Under these conditions, the μmMSC achieved a maximum current density of 144 μA cm−2 and a peak power density of 17 μW cm−2. These results demonstrate that the proposed textile-based μmMSC provides a promising platform for flexible bio-solar energy systems, with potential for wearable applications, while offering improved sustainability and scalability compared to conventional rigid device.

Micromachines doi: 10.3390/mi17050592

Authors: Mehdi Bejani Alessia Galli Riccardo Vettori Marco Mauri Stefano Mariani

Wafer-level testing of Photonic Integrated Circuits (PICs) represents a critical throughput bottleneck in silicon photonics manufacturing, particularly as co-packaged optics demand testing of thousands of optical I/O per wafer. This work introduces optimized alignment algorithms for the Technoprobe Eclipse Dynamic probe card system, which integrates electrical probes and a piezoelectrically actuated fiber array unit within a single probe head, eliminating external positioning equipment. We systematically evaluate seven alignment algorithms: Reference Coarse Scan, Reference Coarse+Fine Scan, Cross Scan, Local and Global Bayesian Optimization, Variable and Fixed Gradient Ascent. The evaluation is made across 72 simulated test cases derived from eight experimental datasets through systematic spatial windowing, combined with experimental validation. Performance is assessed under four operating regimes—high-speed (HS) and low-speed (LS) operation, each with or without hysteresis compensation (H/NH). Experimental validation across eight die positions confirms 100% success rate for both Local Bayesian (98.24% accuracy in 99.87 arbitrary units (a.u.)) and Fixed Gradient (99.18% accuracy in 154.01 a.u.) baseline algorithms. Comprehensive simulation results with improved algorithms across all four scenarios reveal distinct performance characteristics. Fixed Gradient achieves the highest reliability (95.8%) with 99.4% average accuracy across all operating conditions. Variable Gradient provides the fastest alignment (1.18 a.u. in HS-NH) with 90.3% reliability. Local Bayesian demonstrates 94.4% reliability with intermediate performance. Global Bayesian Optimization achieves the best sample efficiency (average 24 steps) but exhibits scenario-dependent reliability ranging from 88.9% (HS-H, LS-H) to 93.1% (LS-NH). For the ideal production scenario, high speed with effective hysteresis compensation (HS-NH), Fixed Gradient emerges as the optimal choice, delivering 95.8% reliability with 1.44 a.u. alignment time, resulting in the best success rate while being nearly as fast as the fastest method. Variable Gradient achieves the absolute fastest alignment (1.18 a.u.) but with 5.5% lower reliability (90.3%), making it suitable only for applications tolerating higher failure rates. Under realistic production conditions with uncompensated hysteresis (HS-H), Fixed Gradient maintains its advantage (95.8% reliability, 3.32 a.u.), while Global Bayesian degrades significantly (88.9% reliability, 4.29 a.u.). Statistical analysis using data profiles validates these methods for high-volume PIC manufacturing, with the Eclipse Dynamic system demonstrating per-die optical alignments in sub-second timescales using open-loop control hardware.

Micromachines doi: 10.3390/mi17050591

Authors: Yulan Liu Yibo Hu Han Xiao Yuanzhen Liu Jing Chen

Offset voltage (VOS) is a critical parameter of sense amplifiers (SAs), determining both the read reliability and performance of SRAM. This paper proposes SC-DISBSA, a low-VOS SA that combines self-adaptive calibration with dynamic body bias technology. Based on the linear relationship between the transfer gate voltage and VOS, a three-step self-adaptive calibration algorithm is established. Supported by the calibration control circuit, this approach quantitatively calibrates circuit mismatch while dynamic body bias further suppresses remaining variations. Under a 28 nm CMOS process, the VOS standard deviation (σOS) of SC-DISBSA remains below 3.1 mV across a 0.7 V to 1.1 V supply range, representing reductions of 49.9% and 69.3% compared to the voltage-latch SA (VLSA) and current-latch SA (CLSA), respectively. At a typical case (TT/0.9 V/27 °C) with a BL differential (ΔVBL) of 6σOS, SC-DISBSA reduces the required bitline discharge delay by 51.7% and improves average read sensing power by 24.9% compared to VLSA. By adopting an non-conventional bitline power supply strategy, SC-DISBSA decreases worst case (FF/1.1 V/125 °C) static power by 36.8% relative to VLSA. Additionally, it reduces gate area by 18.9%. Overall, SC-DISBSA effectively optimizes SRAM read latency and power efficiency.

Micromachines doi: 10.3390/mi17050590

Authors: Jianing Li Yuan Li Kai Peng Xiaoli Lu Xiaohua Ma

Electro-thermal improvement is critical for β-Ga2O3 power devices to mitigate self-heating while maintaining high-voltage capability. Here, we propose a β-Ga2O3 cage-integrated slanted-fin MOSFET (C-SFMOSFET). By optimizing the cage-to-fin and cage-to-drain distances, the cage sequence simultaneously strengthens channel depletion and enhances heat dissipation in the gate-to-drain region. Compared with the baseline slanted-fin MOSFET (SFMOSFET), the proposed 4-cage C-SFMOSFET achieves a 1.75× higher Baliga’s figure of merit and reduces the peak junction temperature by 8 °C at 0.55 W/mm. These results indicate that the proposed device layout can effectively improve device-level electro-thermal performance and further exploit the inherent advantages of ultra-wide-bandgap β-Ga2O3.

Micromachines doi: 10.3390/mi17050589

Authors: Qingming Fan Longfei Liu Guokang Su Chuanyun Zhang Man Zhu Kai Cheng

As one of the most promising new materials in the field of materials science, high-entropy alloys (HEAs) have attracted widespread attention due to the unique structure, exceptional properties and engineering performance, and complex composition. The CoCrFeNiZr0.5 eutectic high-entropy alloys (EHEAs) exhibits excellent high-temperature thermal stability, ductility, creep resistance, and corrosion resistance, demonstrating great potential for applications in marine equipment. This paper explores the engineering feasibility of electrical discharge machining (EDM) of CoCrFeNiZr0.5 EHEAs and investigates the EDM of micro-holes using a hollow copper electrode on a CNC EDM drilling machine under various machining parameters, including different gap voltage, pulse-on time, pulse-off time, and pulse amplifier settings. The effects of these parameters on the inlet diameter, outlet diameter, and recast layer of the micro holes are analyzed. The optimal micro-hole machining parameters are determined by comprehensively considering machining efficiency and electrode wear: gap voltage of 33 V, pulse-on time of 3 μs, pulse-off time of 1 μs, and pulse amplifier output of 3 A. Adopting the parameters to process a button ingot sample with a depth of 5 mm, it was found that the machining speed is 7.79 mm/min and the electrode wear is 1 cm. This research renders the foundation for further development and engineering application of CoCrFeNiZr0.5 EHEAs in the context of high-value material design and manufacturing.

Micromachines doi: 10.3390/mi17050588

Authors: Yu-Ching Weng Chen-Yu Wu

Simultaneous quantification of ascorbic acid, dopamine, and uric acid is crucial for clinical diagnostics. Here, an electrochemical sensor was developed by modifying a glassy carbon electrode with a ternary composite of multi-walled carbon nanotubes, graphene, and Vulcan XC72 carbon black via a simple mixing method. The synergistic interaction of these carbon materials significantly increases the electroactive surface area and introduces defect-driven catalytic sites, enhancing electron transfer kinetics. The sensor enables interference-free simultaneous detection, exhibiting linear ranges of 100–1000 μM ascorbic acid, 5–50 μM dopamine, and 10–100 μM uric acid with sensitivities of 0.044, 0.47, and 0.95 μA μM−1, respectively, and corresponding limits of detection of 34.1, 4.23, and 11.1 μM. The platform also demonstrated excellent stability, reproducibility, and anti-interference performance, with satisfactory recoveries in human urine samples. These results highlight the ternary composite sensor as a reliable and practical tool for multiplexed monitoring in complex physiological matrices.

Micromachines doi: 10.3390/mi17050587

Authors: Yang Li Changkang Fu Hongming Zhang Hongyang Guo Zhiqiang Zhao Mengyang Zhao Ruihong Gao Qiang Wang Chen Wang Caiwen Ma Dong He Yongmei Huang

Tilt-to-length (TTL) coupling is a critical noise source in high-precision interferometric measurements, particularly in systems involving angular actuation and beam steering. This paper proposes a nonlinear cyclic modulation method to identify lateral misalignment and suppress the associated TTL coupling. By applying controlled sinusoidal angular excitation and evaluating the complex modulus ratio between the optical path difference (OPD) and the beam angle at the modulation frequency, the TTL noise induced by the point-ahead angle mechanism (PAAM) is separated and quantified in the frequency domain. Experimental results demonstrate that lateral offset correction reduces TTL noise by 94%, corresponding to a suppression factor of 15.5 and enabling pointing control better than 21 µm/rad. Meanwhile, the parasitic displacement noise of the PAAM is reduced from 10 pm/Hz1/2 to below 4 pm/Hz1/2. These results validate the effectiveness of the proposed modulation-based identification framework and demonstrate its applicability to precision interferometric systems.

Micromachines doi: 10.3390/mi17050586

Authors: Zhaoyun Zhang

Since the publication of the “Review of Embedded Artificial Intelligence Research” in 2023, driven by innovations in hardware architectures, advances in lightweight algorithms, and the maturation of edge–cloud collaboration technologies, embedded artificial intelligence (embedded AI) has progressed from “technically feasible” to “large-scale deployment”. As a continuation of that review, this article systematically surveys the core advances in embedded AI from 2023 to 2026. At the hardware level, it examines engineering progress in non-von Neumann architectures such as compute-in-memory and neuromorphic chips, as well as heterogeneous integration technologies. At the algorithmic level, it covers dynamic adaptive lightweighting, specialized edge-side optimization of large models (including on-device large language model fine-tuning and edge diffusion models), and lightweight multimodal approaches. In terms of deployment paradigms, it discusses edge-side full training, federated edge learning, edge–cloud collaborative intelligence, and emerging paradigms. At the application level, it illustrates the “perception–decision–execution” pipeline in industrial IoT, wearable healthcare, autonomous driving, embodied intelligence, and smart agriculture. The article also analyzes core challenges including ultra-low-power design for extreme scenarios, cross-platform standardization, edge-side data security and privacy, and model robustness in complex environments. Based on these findings, four research directions are proposed to guide future work.

Micromachines doi: 10.3390/mi17050585

Authors: Xuyang Song Jun Zhao Tao Long Chunxiang Ni Xinqing Li Manwen Liu Xuran Zhu Zhiyu Liu Zheng Li

To improve accuracy in calculating the radius of a spiral electrode and the number of turns in existing spiral-type Silicon Drift Detectors (SDDs), in this paper, we propose a method with which to derive first- and second-order approximations of differentiation equations for the spiral angle θ as a function of its radius r(θ) using Taylor expansion. Combining these with formulas for electrode pitch P(r) and width W(r), we developed a simple and physically intuitive method for obtaining a high-precision single-sided hexagonal spiral SDD. Comparisons of spiral structures calculated using the first- and second-order approximation formulas reveal that the second-order approximation yields more spiral turns, thus allowing superior electrical performance, including smoother electric potential profiles, more-uniform electric field distributions, and better-defined electron drift channels.

Micromachines doi: 10.3390/mi17050584

Authors: Guo Chen Xi Chen Ziwen Jin Hongbo Tian Ruipeng Zhao Bowan Tao

Due to the intrinsic fast response characteristic of the atomic layer thermopile (ALTP) structure compared to the conventional thin film thermopile, the ALTP thermal gas flow sensor shows encouraging potential in fast gas flow detection. However, the thermal conduction delay between the ALTP film and the heating film still restricts the response speed. In this work, the prepared Si3N4/AlN composite films significantly reduced the thickness of the insulating layer while ensuring reliable insulation properties. Therefore, the response time of the ALTP thermal gas flow sensor was significantly reduced to 0.1 ms. Meanwhile, the sensor also demonstrated reliable and regular response signals in the tests of different gases, with different thermal sensitivity S*(N2) > S*(O2) > S*(Ar), conforming to the characteristics of thermal gas flow sensors. This work may promote the application of the ALTP sensor in high-speed gas flow detection.

Micromachines doi: 10.3390/mi17050583

Authors: Kai Zhang Zeling Yang Chengxu Zhou Xinwang Cao Xiyuan Feng

This study successfully developed an efficient one-dimensional confinement strategy to encapsulate polyoxometalate NiMo6 clusters densely and uniformly within the cavities of a single-walled carbon nanotube (SWCNT), constructing a unique core–shell NiMo6@SWCNT composite electrocatalyst. Comprehensive characterization including high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible absorption spectroscopy (UV-Vis) systematically confirmed the uniform dispersion and structural integrity of NiMo6 within the SWCNT channels. Key evidence encompasses: (1) EDS elemental mapping revealing high co-localization of Ni/Mo signals inside the lumens; (2) transmission electron microscopy (TEM) images confirming the effectiveness of the filling process. The composite achieved an exceptionally low overpotential of 308 mV to drive a current density of 10 mA cm−2 (significantly outperforming pure NiMo6 at 365 mV and pristine SWCNT at 519 mV), exhibited a remarkably low Tafel slope of 96.64 mV dec−1, possessed a high electrochemical active surface area (10.75 mF cm−2), and very low charge transfer resistance. Critically, it showed negligible current density decay during prolonged chronoamperometric operation over 35,000 s (>9.7 h). This work not only validates the confined encapsulation as a viable strategy for fabricating highly active polyoxometalate/carbon composites, but also elucidates that the performance enhancement stems from a “triple synergy”: the intrinsic catalytic activity of NiMo6, the highly conductive/mass-transport network provided by SWCNT, and the synergistic effects arising from the confined interface—namely stress regulation and electronic coupling. This insight provides a novel perspective for designing high-performance non-precious metal electrocatalysts.

Micromachines doi: 10.3390/mi17050579

Authors: Tomasz Blachowicz Guido Ehrmann Elzbieta Stepula Andrea Ehrmann

Biosensors have a recognition element that detects a bioanalyte as well as a transducer that transfers the measured physicochemical properties into an electric signal, which is amplified, processed, and depicted on a user interface and usually stored in a data storage system. Such biosensors can be used in a broad range of applications, from personalized medicine to drug discovery, and from food safety to plant disease diagnosis. Portable biosensors are often based on microfluidic systems or micro-electromechanical systems (MEMS), measuring physical or chemical parameters. In spite of their importance for diverse applications, there are still several limits regarding the portability of biosensors, which is often necessary. Besides the required miniaturization of the components and the limited lifetime of some biological reagents, sample preparation and handling can be problematic. This review gives an overview of recent biosensor research, concentrating on optical measurements, and shows the possibilities and limits of the biosensors developed during the last few years.

Micromachines doi: 10.3390/mi17050582

Authors: Ana R. Domingues Joana Silva Lara Teles Bernardo S. Dores Alice Miranda Sofia Martinho Jorge Correia-Pinto Bruno Esteves Eliana M. F. Vieira Manuel F. Silva José H. Correia Sara Pimenta

Long-gap esophageal atresia is a congenital anomaly that requires challenging repair procedures that are often associated with complications. This work proposes the use of nitinol to repair long-gap esophageal atresia. A first proof-of-concept with commercial nitinol is presented. Experimental tests and simulations were performed, including the application of electrical currents to promote nitinol heating and consequent contraction, tensile tests, chemical analysis, and ex vivo tests using porcine esophageal tissues. A preliminary experiment is also presented regarding NiTi sputtering deposition and the morphological, chemical, and crystallographic analysis of the thin-films, featuring the implementation of a microfabricated solution. The experimental electrical tests were in accordance with the simulations. The nitinol electrical resistance (0.8–1.5 Ω) decreased as its temperature increased (20–60 °C) with the application of electrical current (<1 A), which was consistent with the experimental Seebeck coefficient (6.49 ± 0.46 µV/K). The measured forces (6.5 N at 45 °C) are also in accordance with traction sutures. Chemical analysis revealed a passive titanium dioxide layer reported for nitinol. Regarding the ex vivo tests, the average nitinol final length was 28.5 mm, below 30 mm (threshold for long-gap esophageal atresia). Finally, preliminary results from NiTi sputtering confirmed well-controlled deposition and the viability of scaling this approach, opening new avenues for nitinol-based biomedical devices.

Micromachines doi: 10.3390/mi17050581

Authors: Rongbiao Yang Tao Jia Jiamin Rong Huanfei Wen Zhidong Xu Zihan Song Enbo Xing Jun Tang Jun Liu

Calcium fluoride (CaF2) crystals are an ideal material for fabricating high-quality whispering-gallery-mode (WGM) optical resonators. However, their hard and brittle nature make it difficult to achieve low-damage, ultra-smooth surfaces through conventional cutting, which limits the optical performance of the resonators. To address this, laser-assisted diamond cutting technology is proposed in this study for low-damage and high-quality fabrication. Molecular dynamics simulations reveal the atomic-scale mechanism by which laser thermal effects reduce cutting forces and promote dislocation motion. Nano-scratch experiments further show that the critical depth of ductile–brittle transition (DBT) increases from 388 nm to 1070 nm, 2.76 times that of conventional cutting. Based on these results, ultra-precision turning of a high-quality hemispherical resonator with a Q factor of up to 1.3 × 108 was achieved. This study provides an effective solution for low-damage and high-performance resonator fabrication from hard and brittle optical crystals.

Micromachines doi: 10.3390/mi17050580

Authors: Jian Dong Bilong Liu Xuxuan Ai Qihang Zhang

In this study, we introduce a novel method for microscale viscosity measurement that eliminates the need for direct contact angle determination. By utilizing a capillary with a sufficiently small radius (R < 0.2 mm), the sharp outlet edge pins the three-phase contact line, stabilizing the apparent contact angle near 90° and nullifying the capillary pressure term. The rheological parameters (K and n) of power-law fluids are then calculated directly by analyzing image sequences of a growing pendant droplet to obtain its volume flow rate Q. Experiments verify through inversion calculation that the apparent contact angle indeed converges to 90° at a small capillary radius. The proposed method is employed to measure 20 wt% and 40 wt% glycerol aqueous solutions (Newtonian fluids) as well as 0.01 wt% and 0.02 wt% xanthan gum aqueous solutions (non-Newtonian fluids). The obtained rheological parameters agree well with reference values within this range, confirming the method’s reliability for these low-viscosity and moderately non-Newtonian fluids. However, measurements on higher concentration fluids (e.g., 0.1 wt% and 0.2 wt% xanthan gum solutions) reveal increased errors, indicating a current limitation in accurately characterizing fluids with high viscosity or pronounced non-Newtonian behavior under gravity-driven flow. This simple technique provides a reliable and low-cost approach for measuring the viscosity of microliter-volume fluids within its characterized operational range.

Micromachines doi: 10.3390/mi17050578

Authors: Xuesong Liu Zhen Guo Fan Du Guokang Su Hua Chen Chuanyun Zhang

To improve the forming quality, precision, and machining stability of square hole structures in high-hardness gun steel (PCrNi3MoVA) during electrochemical machining (ECM). A planar cathode bottom design array with liquid holes is innovatively proposed in this paper to achieve uniform distribution of the flow field in discrete bottom machining gaps. The modeling and simulation of the flow field within the ECM gap were carried out using simulation software. A cathode with 25 outlet holes in an array distribution and a profile thickness of 1 mm was designed. However, sparking occurred on the cathode bottom surface during ECM experiments, leading to machining short-circuit. Further analysis and structural optimization were conducted on the sparking area of the cathode bottom surface. The introduction of flow guide grooves on the cathode bottom surface can effectively improve the uniformity of flow field distribution and the stability of the machining process, thereby solving the problem of manufacturing square holes in high-hardness gun steel materials. Finally, under the conditions of an electrolyte pressure of 0.7 MPa, a machining voltage of 12 V, a frequency of 2 kHz, a duty cycle of 60%, and a feed rate of 0.8 mm/min, a square hole with a side length of 10.2 mm was obtained, with a straightness error of ±0.05 mm and a filet radius of 0.38 ± 0.05 mm.

Micromachines doi: 10.3390/mi17050577

Authors: He Zhou Chao Zhong Lei Qin

In this study, a flexible, lightweight high-frequency underwater transducer (FT) was designed and fabricated. To ensure the flexibility and reliability of the transducer, a flexible piezoelectric composite material with a same-side electrode configuration and a perforated flexible printed circuit (FPC) were designed. First, finite element simulation analysis was performed on the flexible piezoelectric composites to optimize the structural parameters. Next, using a cutting and infusion method combined with reflow soldering, the piezoelectric composites and FPC were integrated to form a flexible sensing element. Finally, a flexible packaging process for the underwater transducer was investigated, resulting in a flexible underwater transducer with a thickness of only 5.3 mm. The results of underwater electroacoustic comparison tests show that the transmission and reception performance of the FT differs by less than 0.5 dB from that of conventional rigid transducers. This demonstrates that the flexible underwater transducer developed in this study not only possesses the advantages of flexibility and can be conformally mounted on curved surfaces but also achieves acoustic performance comparable to that of traditional rigid transducers, thereby providing new insights for the lightweight development of underwater transducers.

Micromachines doi: 10.3390/mi17050576

Authors: Qilin Ren Shuang Ma Jiahao Liu Ya Fan Ying Yu Huilin Mu Sihang Tian

In this paper, we propose a single-layer metasurface structure with ultra-wideband operation and high polarization conversion efficiency, capable of transforming linearly polarized waves into cross-polarized waves. This structure excites additional electromagnetic resonance modes by integrating two symmetrical square patches within an anisotropic split-ring resonator (SRR). These new modes couple with the inherent resonance modes of the SRR, forming closely spaced multi-resonance characteristics across a wide frequency band. This multi-resonance capability enables broadband polarization conversion. This metasurface achieves an ultra-wideband performance spanning 10.89 GHz to 30.12 GHz, covering part of the X-band, the entire Ku-band, and the K-band, while maintaining a high polarization conversion efficiency exceeding 90%. Its broadband characteristics are attributed to the resonator’s ability to generate multiple resonances within a single unit cell. Both experimental and simulation results demonstrate the metasurface’s excellent polarization conversion performance. Furthermore, the proposed metasurface maintains acceptable oblique-incidence performance over a large portion of the operating band, although localized degradation appears at some frequencies. This structure offers significant advantages over traditional multilayer or active designs, featuring simple fabrication without assembly or welding. It may be useful for broadband polarization conversion and may also provide potential for scattering-control applications.

Micromachines doi: 10.3390/mi17050575

Authors: Dalong Liang Wenbin Cui

Constructing inverted wedge-shaped hydrophilic channels with a small apex angle on surfaces with wettability patterns is an effective strategy to promote efficient and complete droplet detachment, which is crucial for applications such as condensation heat transfer and self-cleaning. However, a comprehensive understanding of how wedge geometry parameters affect droplet dynamics has not been established. In this study, we systematically investigate the dynamics of droplet formation and detachment within inverted wedge-shaped superhydrophilic channels fabricated by laser etching on hydrophobic or superhydrophobic substrates. Four distinct droplet detachment mechanisms are revealed. Our results indicate that, within the experimental parameters tested, a slender channel geometry—featuring a narrow upper base, a minimized lower base, and sufficient height—combined with a superhydrophobic substrate, promotes high-position droplet formation, extends the droplet sliding distance, and significantly reduces resistance. This synergy leads to the most efficient detachment mechanism: inertia-driven direct shedding. For the tested configurations, the C1.2/0/40 channel achieved the highest recorded detachment frequency of 318 min−1 at a flow rate of 0.5 mL/min. Furthermore, droplet rebound at the channel tip is observed in some configurations, where two to three droplets must form sequentially and coalesce to trigger a single detachment event. This work provides actionable geometric design strategies for engineering surfaces capable of directional and highly efficient droplet detachment.

Micromachines doi: 10.3390/mi17050574

Authors: Soobin Lee Jidong Jin Zhenyuan Xiao Wensi Cai Zhigang Zang Hyun Seok Lee Jaekyun Kim

Molybdenum disulfide (MoS2) is a compelling candidate for visible-light detection due to its strong optical absorption and tunable bandgap, yet the development of high-performance MoS2 photodetectors remains limited by challenges in scalable integration, low-voltage operation, and efficient photoresponse. Here, we report an ion-gel-assisted transfer strategy that enables the fabrication of large-area MoS2/ion gel films that are suitable for low-power phototransistor applications. The transferred MoS2/ion gel stack is laminated onto an indium-tin-zinc-oxide (ITZO) layer on a glass substrate to fabricate a MoS2/ITZO heterojunction phototransistor, with the ion gel serving as an ultrathin, high-capacitance gate dielectric. The resulting phototransistor exhibits a field-effect mobility of 4.12 cm2/Vs, an on/off current ratio of 4.9 × 105, and a subthreshold swing of 0.17 V/dec. Under 635, 520, and 405 nm illumination with a power density of 4.5 mW/cm2, it achieves responsivities of 0.58, 1.82, and 5.56 A W−1 and detectivities of 5.90 × 109, 1.86 × 1010, and 5.68 × 1010 Jones, respectively. These findings demonstrate that the ion-gel-assisted transfer process offers a robust route to high-performance, low-voltage photodetection and provides a promising platform for next-generation optoelectronic technologies.

Micromachines doi: 10.3390/mi17050573

Authors: Božidar Bratina Dušan Fister Jernej Nezman Jakob Šafarič Riko Šafarič

The new method proposed in this study, featuring a one-finger gripper, uses three types of forces—van der Waals force, capillary force, and coupling force due to ice—to grip and release microobjects to submillimeter-sized objects (5 to 300 µm). The gravitational force of an object can be neglected in the case of microobjects, but this is not the case for submillimeter-sized objects. This is the first reason that we use the coupling force due to ice; the second reason is that the shape of a micro- or submillimeter-sized object does not matter in this case. The usage of all three forces yields greater versatility regarding objects of different sizes and shapes and, consequently, greater overall reliability in gripping or releasing compared with methods that use only one or two of the mentioned forces. In this study, the laboratory set-up involved the active control of the temperature for both the one-finger gripper and the releasing surface for objects from −25 °C to 40 °C in a closed dust-free chamber in atmospheric air at relative humidity (RH) = 30%. A relatively low RH was achieved with the RH controller, enabling the release or grip procedures to last approx. 2–3 s for microobjects and 6 s for submillimeter-sized objects with the same equipment.

Micromachines doi: 10.3390/mi17050572

Authors: Manon Marchandise Adam Chafai Christophe Caucheteur Pierre Lambert

This paper presents a force sensor made of a compliant glass mechanism instrumented with a waveguide and a Bragg grating, measuring the reflected wavelength shift produced by the strain in the compliant element generated by the applied force. The compliant element geometry and material have been chosen for the sensor to be spliced or manufactured at the extremity of an optical fiber, enabling possible insertion of the instrument in the bronchial tree after embedding in a proper catheter. The context of this research is the mechanical discrimination between healthy and cancerous lung tissues based on their mechanical signature. The paper proposes a comprehensive study including the mechanical design of the structure and the optimization of the production parameters, thanks to an experimental parametric study. After experimental characterization of the mechanism stiffness, the optical response to a mechanical force is reproduced with two different samples on two different days (more than 25 repetitions). The conclusion is that a fair linear and repeatable response is observed (±26 mN) for forces ranging from 0 to 250 mN.

Micromachines doi: 10.3390/mi17050571

Authors: Xingyu Pi Jiao Li Hongyu Chen Chunming Ren Zhuoqing Yang Chong Lei Aiying Guo Xuecheng Sun

As a core component in electronic circuits, the size of inductors is crucial for the thin-film integration and miniaturization of circuits. Although various miniaturized inductors have been fabricated by using integrated circuit technology, their low current-carrying capacity and small inductance values cannot meet current application requirements. Therefore, this paper designs an inductor chip based on a double-layer parallel (DLP) array microcoil structure. Experimental verification demonstrates that the developed DLP inductor exhibits a far superior rated energy storage capability per unit area compared to other single-layer inductors, along with excellent thermal performance. Meanwhile, the 4 × 3 DLP array can withstand a maximum DC current of 4.25 A. This structural innovation provides a meaningful thermal–electromagnetic co-design reference solution for highly reliable integrated power modules.

Micromachines doi: 10.3390/mi17050570

Authors: Mohammad Faisal Ahmed Kyle Primes

The auxetic reentrant structure, one of the most widely studied negative Poisson’s ratio structures for its geometric simplicity, has long seen limited applications due to challenges emanating from its inherent design when built from a single rigid or flexible material. This paper aims to address these challenges by taking advantage of dual-material extrusion technology and density gradient design strategy. Two density gradient reentrant auxetic structures are proposed and fabricated using material extrusion additive manufacturing in single-material (flexible) and dual-material (rigid/flexible) modes, with the introduction of a novel dual-material interface design. In-plane compression tests are carried out to assess the energy absorption characteristics of the structures. The results show that dual-material structures exhibit higher yield stress, mean crushing force, peak crushing force, and maximum crushing force, as well as superior specific energy, energy dissipation, and energy release compared to single-material structures. Dual-material structures also demonstrate high lateral stiffness, minimizing elastic instability, a highly desirable feature for reusable energy-absorbing structures with high shape recovery capability. The results substantiate the significance of the synergy between the dual-material and density gradient designs proposed in this study. Overall, the key findings of the study may serve as a reliable reference for the design of future lightweight energy-absorbing structures.

Micromachines doi: 10.3390/mi17050569

Authors: Angelina Lin Joanna Tang Chunlian Zhong Shanshan Yao Zhaoqing Cong

Therapeutic interventions within the urinary system are often limited by the complex and tortuous anatomy of the renal pelvis and ureters, restricting access to deep regions and increasing the risk of mucosal trauma. In this study, we present a multifunctional, magnetically controlled ferrofluid droplet robotic platform engineered for high deformability and precision navigation. A custom electromagnetic actuation system was developed and optimized via COMSOL Multiphysics (version 6.3, COMSOL Inc., Stockholm, Sweden) simulations to generate programmable magnetic fields. Experimental validation in both simplified environments and anatomically realistic 3D-printed urinary tract models demonstrated the droplets’ capacity for controlled locomotion, reversible deformation, and traversing constrictions significantly smaller than their resting diameter. The droplets’ locomotion and extreme deformability are governed by the dynamic balance between the applied magnetic gradient forces, the restoring interfacial tension of the ferrofluid, and the fluidic viscous drag. Quantitatively, the droplets achieved robust translational velocities up to 260 mm/s under single-coil actuation (51 mT, 20 Hz) and 108 mm/s under a more stable dual-coil configuration (51 mT, 8.3 Hz). Furthermore, two clinically relevant functionalities were successfully executed: rapid vibration-induced release of encapsulated dye for targeted drug delivery, and the precise mechanical capture and transport of artificial kidney stones. These results establish a highly versatile platform for minimally invasive urological procedures, highlighting the immense potential of soft magnetic microrobotics for integrated therapeutic applications.

Micromachines doi: 10.3390/mi17050568

Authors: Shichao Zhu Mieradilijiang Abudupataer Zheng Zuo Yongxin Sun Ben Huang

We developed a multi-channel and multilayered polydimethylsiloxane (PDMS) microfluidic platform that integrates cyclic mechanical stimulation, independent reagent delivery, and real-time optical observation within a single device. The platform employs a four-layer architecture comprising a pneumatic valve control layer, an observation channel for cell culture and imaging (24 mm × 4 mm), a medium perfusion layer with independent inlet ports, and a vacuum actuation layer that deforms a 200 μm PDMS membrane under −20 kPa cyclic pressure at 1 Hz. Cyclic membrane strain of 10% was calibrated using fluorescent bead tracking and image analysis. Finite element analysis based on nonlinear Föppl–von Kármán plate theory confirmed that the central cell culture region (60% of membrane area) exhibits a mean von Mises strain of 14.2% with a uniformity of 81.3% (CV = 18.7%), validating relatively uniform mechanical stimulation across the culture surface. As a proof-of-concept, human aortic smooth muscle cells (CRL-1999) cultured under cyclic strain showed significant upregulation of HIF-1α expression (2.5-fold, p<0.01) and pronounced F-actin stress fiber alignment visualized by fluorescence microscopy, confirming the platform’s capability for mechanotransduction studies and real-time cellular observation. The multi-channel architecture enables multi-condition parallel testing by simultaneously introducing different reagent concentrations through independent inlet ports while maintaining identical mechanical parameters across all channels, providing a versatile tool for systematic investigation of cellular responses under controlled biomechanical conditions.

Micromachines doi: 10.3390/mi17050567

Authors: Hanbo Xu Mingyang Zhu Zeen Fang Lei Zhang

Indium oxide (In2O3) has recently emerged as a promising semiconductor for advanced electronics due to its high electron mobility and wide bandgap. In this article, the lateral scaling characteristics of top-gate In2O3 thin-film transistors (TFTs) featuring a 1.5 nm thick channel and a 7 nm thick HfO2 gate dielectric are investigated by two-dimensional device simulation. The analysis covers short-channel effects, DC characteristics, transconductance behavior, and small-signal radio frequency (RF) metrics across a gate-length (LG) range of 20 nm to 700 nm. Simulation results identify a critical gate length near 100 nm for the transition from long-channel to short-channel behavior. For LG ≤ 100 nm, pronounced short-channel effects emerge, featuring a significant negative VTH shift and a drain-induced barrier lowering (DIBL) coefficient up to ~130 mV/V. A non-classical gm scaling behavior is observed, where gm_max initially increases with LG, then remains within a narrow range and eventually evolves toward the conventional long-channel trend. Further analysis of the lateral electric field distribution, field-dependent mobility, and transconductance efficiency indicates that this behavior originates from a crossover between short-channel field-assisted transport and gate-controlled channel modulation. The devices show strong RF potential, with fT and fmax reaching 124.32 GHz and 157.64 GHz, respectively, at LG = 20 nm. The high-mobility In2O3 channel leads to a less distinct fT scaling transition from the classical 1/L2G dependence to the short-channel 1/LG dependence, while fmax scaling evolves through different regimes governed by capacitance-related limitations, intrinsic transport enhancement, and short-channel non-idealities. This work provides physical insight into the lateral scaling behavior of ultrathin top-gate In2O3 TFTs and highlights their potential for high-frequency and power-dense applications.

Micromachines doi: 10.3390/mi17050563

Authors: Yiqing Wei Zhensen Gao Haixia Li Zhibin Li

This work proposes a polarization-insensitive scalable wide-angle metasurface array for highly efficient ambient energy harvesting in the 5.8 GHz Wi-Fi band. Inspired by dipole antenna principles, we design an asymmetric planar orthogonal dipole-based metasurface featuring monolithic integration of Schottky diodes (HSMS-2860) at unit cell feed gaps. This novel direct-impedance-matching strategy eliminates conventional matching networks, reducing energy conversion losses while enabling 99% radiation-to-AC efficiency across all polarization angles at 5.8 GHz. The coplanar architecture interconnects metasurface unit cells via inductors, simultaneously establishing low-loss DC channels and suppressing RF leakage. Fabricated as a 5 × 5 array, the prototype achieves 77.9% peak RF-to-DC efficiency with polarization insensitivity at an incident power of 25 dBm. Furthermore, with incident powers of 15 dBm and 20 dBm, the proposed metasurface array attained RF-to-DC conversion efficiencies exceeding 40% and 60%, respectively. This result indicates that the array is capable of achieving high energy harvesting efficiency across a broad power range. This scalable, drill-free, and polarization-insensitive design demonstrates strong potential for harvesting ambient RF energy in real-world multipath environments.

Micromachines doi: 10.3390/mi17050564

Authors: Pei Yin Dongliang Jia Dan Tan Rusen Yang

The dielectric response provides an integral description of polarization mechanisms across frequency ranges and constitutes a key physical basis for understanding ferroelectric behavior. Here, we systematically investigate the broadband dielectric response of Group-II metal oxide (BeO, MgO, CaO, ZnO, and CdO) monolayers using first-principles calculation. In the low-frequency regime, ionic polarization governs the dielectric response. A distinctive feature is the LO–TO degeneracy at the Γ point accompanied by a V-shaped nonanalytic LO phonon dispersion. d-state hybridization increases with the metal atomic number, resulting in higher Born effective charge, which works together with phonon softening, reduced mass and unit cell area to significantly strengthen the ionic dielectric contribution. The quasiparticle band gap decreases with the metal atomic number, driving redshifts of the dielectric function and wide band optical response from the deep-ultraviolet to the near-infrared. Particularly, CdO exhibits the strongest electronic polarization, with an optical dielectric constant of 2.68 and a static refractive index of 1.64. This work establishes a complete dielectric spectrum from ionic to electronic polarization, providing theoretical guidance for polarization engineering and design of two-dimensional ferroelectric devices.

Micromachines doi: 10.3390/mi17050566

Authors: Aayush Madan Wenyu Jiang Yixin Wang Yaowen Yang Jianzhong Hao Perry Ping Shum

Tube boilers are extensively employed in oil and gas refineries, as well as in petroleum, energy, and power generation industries, where they serve critical functions in local steam-generation units and combined-cycle gas turbine (CCGT) plants. However, these boilers are prone to defects arising from waterside corrosion (e.g., thinning of U-bend tubes), fireside corrosion, and material degradation caused by stress or creeping. Among these issues, wall thinning of tube bends is particularly severe, as it results in localized metal loss, reduced structural integrity, and an elevated risk of tube rupture or failure under high-temperature and high-pressure operating conditions. Such failures can significantly compromise boiler safety and efficiency, potentially leading to forced outages, costly unplanned repairs, or catastrophic damage if not detected in time. The current condition-monitoring policy for U-bends relies on scheduled preventive maintenance and unscheduled corrective interventions. In practice, this involves randomly checking approximately 10–20% of the tubes through spot scanning, partial scanning, or full scanning, with repairs typically carried out only after an undetected failure occurs. Such maintenance strategies generally require plant shutdowns, making the process time-consuming, labor-intensive, and ultimately not cost-effective. This paper reviews existing solutions, technologies, and research addressing the problem, and introduces femtosecond laser micromachined fiber optic sensors as a transformative approach for real-time monitoring of wall thickness reduction in U-bend boiler tubes, thereby opening pathways for further research.

Micromachines doi: 10.3390/mi17050565

Authors: Jing Chang Shixuan Wang Shizhen Liang Xihao Feng Wei Zhao

Fueled by the push for “More than Moore”, three-dimensional integrated circuits (3D ICs) have become a backbone of next-generation electronics. Their complex architectures place unprecedented demands on etching technologies, which must now deliver atomic precision, stringent high-aspect-ratio (HAR) control, and virtually damage-free profiles. Meeting these challenges requires metrology capable of true 3D, quantitative analysis at the nanoscale. Atomic force microscopy (AFM) has proven essential in this regard, offering non-destructive, sub-nanometer characterization that other techniques cannot provide. This review systematically examines AFM’s pivotal role in advancing key etching processes for 3D ICs, including deep reactive ion etching of through-silicon vias (TSVs), atomic layer etching (ALE), and cryogenic plasma etching. We detail AFM’s unique contributions to quantifying sidewall roughness, verifying etch-per-cycle rates, and assessing surface damage. We also discuss how recent innovations, such as tilting-AFM, HAR probes, and automated inline systems, are overcoming traditional barriers in throughput and access to sidewalls and deep trenches. Looking forward, the integration of AFM with optical metrology, machine learning, and multi-scale modeling opens a path toward truly autonomous process control and optimization. As such, AFM stands as an indispensable tool for developing and refining the etching processes that underpin next-generation 3D semiconductor manufacturing.

Micromachines doi: 10.3390/mi17050561

Authors: Chun-Jui Chen Jae-Sung Kwon Han-Sheng Chuang

The rapid and precise detection of biomarkers and pathogens remains a critical challenge in clinical diagnostics. Traditional methodologies are frequently hindered by protracted workflows, complex sample preparation, and reliance on resource-intensive instrumentation. Acoustofluidics—the synergistic integration of acoustics and microfluidics—has emerged as a transformative solution for point-of-care testing (POCT). Bulk acoustic wave (BAW) and surface acoustic wave (SAW) technologies enable the contactless, label-free, and biocompatible manipulation of bioparticles across micro- and nanometer scales. This review critically examines recent advancements in BAW- and SAW-based acoustofluidic biosensors. We elucidate the fundamental principles governing distinct acoustic modes—including Quartz Crystal Microbalance (QCM), film bulk acoustic resonator (FBAR), and Solidly Mounted Resonator (SMR) for BAW and Rayleigh and Love waves for SAW—and evaluate their specific roles in liquid-phase sensing, particle sorting, and cellular focusing. Results show that integrating on-chip sample preparation accelerates diagnostic workflows, reducing assay times to under 10 min. Coupling acoustic manipulation with optical, mass-based, or electrochemical modalities effectively overcomes fundamental diffusion limits, achieving ultrasensitive, multimodal detection. We address translational challenges—acoustothermal heating, biofouling, and scalable integration. Following a discussion of clinical applications in oncology and infectious diseases, we map emerging trajectories, emphasizing AI-driven intelligent microfluidics, modular architectures, and flexible wearable platforms that will ultimately democratize continuous precision diagnostics.

Micromachines doi: 10.3390/mi17050562

Authors: Qiyuan Zheng Jin Meng Li Wang Zhaoyue Wang

Conventional terahertz (THz) radio frequency (RF) frontends struggle to simultaneously balance the high performance and miniaturization of monolithic integrated designs with the excellent testability of discrete modular architectures. This paper presents a detachable 183 GHz terahertz RF frontend and completes the module design and system integration of a low-noise amplifier (LNA) and a second-order subharmonic mixer. Through optimization of the waveguide-to-microstrip transition, parasitic compensation for pad bonding, and the structural design of the chip shielding cavity, combined with a high-precision alignment scheme using positioning pins and screws, the integrated module achieves detachability, testability, and ease of maintenance. Measurement results show that across the 160–200 GHz frequency band, the amplifier achieves an average gain of 16.51 dB; the mixer exhibits a minimum conversion loss of 8.62 dB; and the full-link noise figure of the system reaches 6.68 dB. The proposed scheme effectively addresses the engineering challenges of conventional integrated architectures and provides a practical implementation pathway for terahertz communication and remote sensing detection frontends.

Micromachines doi: 10.3390/mi17050560

Authors: Jingjing Zheng Qian Wu Zhenheng Lin Xuejia Hu Liqing Qiao Genliang Li Jinkun Luo

Separating plasma from small-volume blood samples is important for rapid blood analysis in point-of-care testing. Microfluidic approaches provide flexible platforms for plasma extraction, but many methods either require complex pretreatment or rely on sheath-assisted or multi-step operations. In this study, we present an acoustofluidic platform that enables sheath-free three-dimensional (3D) focusing of blood cells and downstream plasma extraction in an integrated microchip. The device employs symmetric cavity-trapped bubbles to generate acoustic streaming under acoustic excitation, thereby reconstructing the local flow field and driving suspended cells toward a stable central region of the channel. Based on this mechanism, blood cells are concentrated toward the middle outlet, while plasma is collected from the two side outlets. The device remains operable over a range of inflow conditions through acoustic-voltage adjustment. Using diluted simulated blood samples, the platform achieved a plasma recovery of approximately 71% and a plasma purity of approximately 99%. In addition, cell-viability tests indicated good biocompatibility under the tested operating conditions. Owing to its simple structure, integrated design, and sheath-free operation, this platform shows potential for future miniaturized sample-preparation applications. However, further validation using real whole blood and clinically relevant plasma-quality metrics will be required in future studies.

Micromachines doi: 10.3390/mi17050559

Authors: Daniel O. Reddy Malek Hassan Jonathan O. Graham Jared Viggers Katherine E. Williams Randy E. Ellis Thomas R. Covey Jacob T. Shelley Richard D. Oleschuk

The use of dried matrix spots (DMSs) has recently re-emerged as a useful sample storage technique and analytical platform along with the increased adoption of and general preference for ambient ionization mass-spectrometric methods. However, challenges associated with precise liquid confinement and sample targeting persist. In this paper, we present a laser micromachining-based approach to prepare DMSs on hydrophobic paper substrates that include visual recognition elements, or reticles, around surface energy traps (SETs). This targeted DMS substrate is combined with direct mass spectrometric analyses, namely liquid microjunction–surface sampling probe–mass spectrometry (LMJ-SSP-MS) and flowing atmospheric-pressure afterglow–mass spectrometry (FAPA-MS). With the laser-based micromachining approach, DMSs flanked by crosshairs for enhanced visualization are prepared on SETs as small as 0.55 mm in diameter, which offers an approximately 12-fold reduction in size compared to traditional DMS preparations. The DMSs prepared on these targeting SETs are demonstrated with the detection of caffeine in model aqueous and artificial urine solutions using LMJ-SSP-MS and FAPA-MS, respectively. With further refinement, this approach could be automated using computer vision and robotics to broaden the scope of DMSs and improve the analytical workflow.

Micromachines doi: 10.3390/mi17050556

Authors: Hanbin Qu Xiaopeng Zhang Sixin Gao Silu Yan

Conventional optimization algorithms face challenges such as lengthy computation times, premature termination at non-convergent points, and the generation of local optima when addressing multi-objective optimization. A multi-objective optimization method based on the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is proposed for optimizing Doherty power amplifier circuits. The pre-layout simulation results show that, compared to traditional design methods, the optimized Doherty power amplifier circuit achieves a 6.4% increase in saturation efficiency, a 3.3% increase in 6 dB roll-off efficiency, and a 1 dB increase in saturation output power at 2.63 GHz. This approach enables multi-objective optimization design for more complex PA circuits and enhances the overall circuit performance.

Micromachines doi: 10.3390/mi17050558

Authors: Qidong Li Yuxin Zhang Baoqiang Huang Weihua Zhang Chen Chen Jianming Lei Desheng Zhang Run Min Qiaoling Tong

Silicon carbide (SiC) MOSFETs are promising for high-efficiency, high-power-density power conversion owing to their high breakdown capability, fast switching speeds, and low switching losses. However, parasitic parameters can cause severe voltage/current overshoot and oscillation during high-speed switching, leading to electromagnetic interference and degraded performance. To address this issue, this study analyzes the mechanisms of current overshoot during turn-on and voltage overshoot during turn-off, and presents an adaptive active gate driver chip based on a three-stage driving current control strategy. By identifying key switching intervals and regulating segmented gate-drive current, the proposed chip can effectively suppress overshoot while reducing the switching loss. During turn-on, cross-cycle switching point regulation based on Miller plateau tracking is proposed to achieve adaptive control under different operating conditions, while the turn-off control is realized by peak sampling of the drain–source voltage. The chip was fabricated in the 180 nm BCD process. Compared with a conventional passive driver, the proposed driver reduces turn-on loss by 35.1% at 400 V/40 A under a dvDS/dt of 4.8 V/ns and reduces turn-off loss by 33.2% under a vDS overshoot of nearly 50 V. These results show that the proposed chip improves SiC MOSFET switching performance and provides a practical gate-driving solution.

Micromachines doi: 10.3390/mi17050557

Authors: Enqing Su Junwei Wang Weijie Sheng Yi Mou Teng Li Jianguo Liu

In complex marine environments, achieving low-cost, highly reliable, and continuous navigation is crucial for the intelligent and autonomous operation of unmanned surface vehicles (USVs). Currently, the integrated Global Navigation Satellite System and Strapdown Inertial Navigation System (GNSS/SINS) serves as the primary navigation architecture for USVs. While the cost of high-performance GNSS receivers has steadily decreased, high-precision SINS remains prohibitively expensive. Consequently, micro-electromechanical system (MEMS)-based SINS has emerged as a preferred alternative due to its favorable balance of cost, power consumption, and size. However, significant inertial sensor errors make it difficult to maintain high-precision positioning during GNSS outages. To address this limitation, the single-axis rotational inertial navigation system (SRINS) has been introduced. Nevertheless, constrained by the single-axis mechanical structure and complex sea state disturbances, the system still struggles to effectively modulate random errors and azimuth gyroscope drift, rendering it insufficient for highly demanding navigation tasks. To overcome these bottlenecks, this article systematically reviews four core technologies: (1) Comprehensive denoising and temperature drift compensation techniques for MEMS gyroscopes; (2) rapid moving-base initial alignment models under high sea state disturbances; (3) fast online calibration methods for azimuth gyroscope drift; and (4) adaptive and robust GNSS/SINS integration architectures capable of accommodating high-dynamic conditions and non-Gaussian interference. Finally, this article discusses the engineering conflict between deploying high-precision algorithms and the limited onboard computational capacity of USVs. It concludes by highlighting a highly promising navigation paradigm for future research: the integration of factor graph optimization with physics-informed deep learning.

Micromachines doi: 10.3390/mi17050555

Authors: María Claudia Rivas Rivas Ebner Seong-Wan Kim Giyeon Yu Emmanuel Ackah Hyun-Woo Jeong Kyung Min Byun Young-Seek Seok Seung Ho Choi

Cardiac auscultation remains a widely used non-invasive method for assessing cardiac function; however, conventional acoustic stethoscopes are limited by subjective interpretation and lack of digital signal-handling capabilities. This study presents the design and fabrication of a chitosan-based diaphragm digital stethoscope using a biopolymer-derived acoustic interface. Chitosan was extracted from mealworm larvae shells through sequential chemical processing and subsequently processed into a glycerol-plasticized film via solution casting to obtain a flexible diaphragm. The mechanical properties of the diaphragm were evaluated to assess its suitability for acoustic applications. The diaphragm was mechanically coupled to a piezoelectric sensor and integrated into a custom 3D-printed chest piece connected to a microcontroller-based acquisition system. Heart sound signals were acquired from four conventional auscultation sites (aortic, pulmonic, tricuspid, and mitral regions). The recorded signals were processed using band-pass filtering, envelope extraction, and time–frequency analysis to visualize waveform morphology and frequency content. The signals obtained exhibited temporal and spectral features consistent with reported phonocardiography characteristics, including identifiable S1 and S2 components. These results demonstrate the feasibility of using chitosan-based diaphragm materials for heart sound acquisition in a digital stethoscope configuration, providing a low-complexity platform for further development of biopolymer-based acoustic sensing devices.

Micromachines doi: 10.3390/mi17050554

Authors: Jiyong Chung Hoyeon Shin Seonho Shin Yeonggi Kim Saeed Zeinolabedinzadeh Dongjin Ji Ickhyun Song

In this paper, we present a study on the automated design optimization of a wideband low-noise amplifier (LNA) operating in Ku-band (12 to 18 GHz) using proximal policy optimization (PPO), one of the widely applied reinforcement learning (RL) algorithms for engineering problems. As a target microwave active circuit, we select a two-stage LNA architecture, where transmission lines (TLs) are dominantly used for impedance matching and gain/noise optimization. For simplicity, all widths of TLs were fixed so that the characteristic impedance is 50 Ω, with lengths of TLs being set as design parameters. In addition, dimension variables of capacitors were treated as design parameters and, in total, we optimized 29 parameters. For target specifications, we set both S11 and S22 to be below −10 dB over the 12–18 GHz band and the noise figure (NF) to be below 2 dB. A total of 20,140 simulations were performed for training and the overall process took about 24 h. The results show that both the reward and the loss converged appropriately, achieving the target specifications successfully. For the final results, we performed up to 25 predictions, and the prediction process was terminated early if a solution meeting all target specifications was found within the given number of attempts. The device model used was a commercial 150 nm GaN high-electron-mobility transistor (HEMT) process technology.

Micromachines doi: 10.3390/mi17050553

Authors: Guangye Jia Qiang Zhou Huayang Zhao

To address the issue of traditional bistable vibration energy harvesters (BVEHs) being prone to becoming trapped in a single potential well—which results in a narrowed energy harvesting bandwidth and reduced efficiency—this paper proposes a method that utilizes the nonlinear electromagnetic force generated during the induction process to modulate the kinematic behavior of the oscillator. The characteristics and influencing factors of the nonlinear force produced during electromagnetic induction are analyzed. A dual-cantilever beam structure is designed, with an iron-core coil and a magnet placed at the respective free ends. A mathematical model of a piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester is established and numerically simulated. Furthermore, a vertical vibration experimental platform is constructed to conduct frequency sweep tests. The experimental results demonstrate that the proposed piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester effectively improves energy harvesting efficiency. Within the frequency range of 5–20 Hz, the system exhibits two vibration modes, with resonant frequencies of approximately 7.7 Hz and 15.7 Hz. For a single-layer PVDF piezoelectric film, the maximum output power at the first and second resonance points is 8.9 μW and 9.7 μW, respectively. The electromagnetic module achieves maximum output powers of 0.39 W and 0.71 W. Moreover, within the frequency ranges of 6.3–9.8 Hz and 14–17.7 Hz (a total bandwidth of 7.2 Hz), the device maintains a stable power output. The effective bandwidth is broadened by approximately 80%, demonstrating excellent broadband performance.

Micromachines doi: 10.3390/mi17050549

Authors: Chunxiang Ni Tao Long Jun Zhao Xuyang Song Xinqing Li Manwen Liu Zhiyu Liu Xuran Zhu Zheng Li

This paper proposes a sectional-chain silicon drift detector (SDD), featuring an elliptical-shaped voltage divider resistor chain, that can address the issue with traditional concentric ring SDDs, which cannot independently provide voltage division. The study replaces the conventional linear voltage divider with an elliptical structure, using its diversity geometry to improve the uniformity of the electric field distribution within the detector’s sensitive area, effectively solving the problem of distortions of edge electric fields and those between the SDD’s cathode rings in traditional structures. The relevant parameters of the elliptical resistor chain are calculated through formulas, which establish a quantitative relationship between the resistance values and the elliptical geometric dimensions, providing a theoretical basis for electric field uniformity control. A device physics model is then established using TCAD for simulation analysis to obtain key performance parameters: the electric potential and electric field distribution inside the detector, the spatial distribution of electron concentration in the detector bulk, and the electric potential gradient on the detector surface. These parameters provide a design reference for the application of high-performance SDDs in fields such as X-ray energy spectroscopy nuclear physics experiments and space radiation monitoring.

Micromachines doi: 10.3390/mi17050552

Authors: Chunmei Wang Qianshu Yu Shuangsheng Zhang Guoliang Zhang Jiang Wu

According to the complementary advantages of the composites, the degradation rate, biological activity and physical and chemical properties of the composites were adjusted by using the hydrophilic and bioactive advantages of soy protein isolate (SPI) on the basis of toughening PLA by polycaprolactone (PCL). In this study, soy protein isolate/polylactic acid–polycaprolactone (SPI/PLA–PCL) composite microspheres were fabricated via double emulsion–solvent evaporation. SPI was introduced to regulate hydrophilicity, biodegradation, and bioactivity based on PCL–toughened PLA. The microspheres were characterized by SEM, EDS, FTIR, and XRD. Hydrophilicity, thermal stability, and degradation behavior were evaluated via water contact angle, TG/DTA, and in vitro degradation assays. Biocompatibility, hemocompatibility, and osteogenic activity were assessed through cell adhesion, hemolysis, CCK–8, ALP, alizarin red staining, and mineralization tests. Results confirmed the successful preparation of SPI/PLA–PCL microspheres. SPI incorporation enhanced hydrophilicity, degradation rate, and cell adhesion. The composite microspheres exhibited favorable thermal stability, hemocompatibility, biocompatibility, and osteogenic induction. The 50% SPI/PLA–PCL group performed optimally in cell proliferation, adhesion, ALP activity, and mineralization, demonstrating promising potential for bone tissue engineering applications.

Micromachines doi: 10.3390/mi17050551

Authors: Xiuquan Zhang Haoyang Du Dawei Cao Jialu Duan Qian Wang Zhenyu Li Wen Hu Guiyin Liu Lei Wang

We demonstrate efficient and thermally stable second-harmonic generation (SHG) in x-cut thin-film lithium tantalate (TFLT) ridge waveguides via modal phase matching (MPM). The experimental characterizations reveal a normalized conversion efficiency (NCE) of 17.2% W−1 cm−2 in a 4 mm long waveguide. Notably, the device exhibits a temperature-dependent phase-matching wavelength slope of 0.007 nm/°C, which shows a two-orders-of-magnitude improvement in thermal stability over conventional periodically poled lithium niobate/lithium tantalate optical devices. Our work indicates that MPM in TFLT is an attractive strategy for integrated nonlinear optical applications, particularly for the on-chip frequency conversion of both classical and quantum light signals without on-chip domain-poling processes.

Micromachines doi: 10.3390/mi17050550

Authors: Shimin Yang Yugang Zhao Qilong Fan Li Guo Zhi Qi Kai Xing Yusheng Zhang

L605 cobalt-based superalloy is a typical difficult-to-machine material because of its high strength, pronounced work hardening, and low thermal conductivity. To improve the microgroove machining performance of this alloy, a self-developed water-jet-guided laser (WJGL) system equipped with a multi-focus lens was employed, and single-factor experiments together with a Box–Behnken response surface design were conducted to investigate the effects of laser power, pulse frequency, water pressure, and feed speed on microgroove depth. The results showed that microgroove depth increased with laser power, decreased with pulse frequency and feed speed, and first increased and then decreased with water pressure. Analysis of variance demonstrated that the developed quadratic regression model was significant and fit the data well. A recommended parameter combination of 274.9 W laser power, 3334.9 Hz pulse frequency, 1.636 MPa water pressure, and 0.107 mm/s feed speed corresponded to a predicted microgroove depth of 621.2 μm. Validation experiments yielded an average microgroove depth of 600.2 μm, with a relative error of 3.4%, indicating that the model can be used for microgroove depth prediction and parameter selection in WJGL machining of L605 alloy and may provide guidance for future multi-objective optimization considering both machining quality and efficiency.

Micromachines doi: 10.3390/mi17050547

Authors: Minhoo Chung Changkyoo Park

This study applies selective laser melting (SLM) to fabricate stainless steel 316L (SS316L) structures on the distribution plate of a Venturi-type nozzle in a pressurized dissolution microbubble generator. SLM is employed because the fabricated structures are approximately hundreds of micrometers in size, making them difficult to produce using conventional milling or other machining methods. These structures are designed to enhance cavitation and gas–liquid interaction, thereby enhancing microbubble generation. Various conditions of the SLM process are conducted, and the combination of 140 W laser power, 100 mm/s scan speed, 30 µm layer thickness, and 120 µm hatch distance achieves the highest relative density while maintaining the austenite phase of SS316L, thus being selected as the optimal SLM process parameters. Microbubble generation test are conducted under three different dissolution tank pressure conditions (0.20, 0.25, and 0.30 MPa) using nozzles with and without the SLM structures. The generated microbubbles in both nozzles ranges from 1 to 110 µm, satisfying the size conditions for microbubbles. The average microbubble size is smaller in the SLM-assisted nozzle (31.8 µm) compared with the plain nozzle (38.8 µm). Furthermore, under the dissolution tank pressure of 0.30 MPa for 30 s, the SLM-assisted nozzle generates a maximum of 52,368 microbubbles, representing approximately a 102.1% increase compared with the plain nozzle (25,907 microbubbles). These results demonstrate that incorporating SLM structures to Venturi-type nozzle effectively enhances microbubble generation, offering promising potential for applications in water treatment, biomedical processes, and chemical engineering.

Micromachines doi: 10.3390/mi17050548

Authors: Thirukumaran Periyasamy Shakila Parveen Asrafali Jaewoong Lee

Electrocatalytic water splitting powered by renewable energy is a promising route for sustainable hydrogen production. Rather than developing separate catalysts for HER and OER, recent efforts focus on multifunctional electrocatalysts that can efficiently drive both reactions, simplifying system design and improving efficiency. A major limitation of conventional water splitting is the high overpotential and low-value oxygen production in OER. To overcome this, hybrid water splitting replaces OER with more valuable oxidation reactions, such as pollutant degradation or organic upgrading, enhancing overall energy and economic efficiency. This review covers the fundamentals of water splitting and highlights key physicochemical techniques for probing electrocatalyst activity, particularly structural reconstruction under operating conditions. It evaluates noble-metal, nonprecious-metal, and metal-free nanocarbon catalysts in both acidic and alkaline media, with emphasis on their roles in alternative anodic reactions. Finally, it outlines current challenges and future directions for developing efficient, durable, and sustainable electrocatalysts for advanced hydrogen production systems.

Micromachines doi: 10.3390/mi17050546

Authors: Mengjiao Lu Zerui Jin Wanjun Wang Jianghai He Qingqing Liu

Plasma etching is a critical step in semiconductor manufacturing, yet existing approaches are either computationally expensive or limited to predicting scalar etching metrics rather than full profile evolution. We propose EPreNet, a condition-guided spatio-temporal network for pixel-level prediction of plasma etching profile evolution from historical profile frames and process parameters. To support this task, we construct a benchmark dataset of 18,360 images spanning 918 process conditions simulated via TCAD, sampled with Latin Hypercube Sampling to ensure uniform parameter-space coverage, and further establish an evaluation framework combining image-level and geometry-based metrics for etching-profile prediction. Experiments demonstrate that EPreNet reduces MSE by 16% and achieves SSIM of 0.992 and PSNR of 30.323 dB, while achieving manufacturing-relevant geometric accuracy with 1.4° sidewall angle error and 1.6% depth error rate. Inference requires only 38.92 ms per frame faster than TCAD simulation 1300 s, supporting rapid surrogate-based evaluation and accelerated TCAD-assisted process exploration. The model also shows strong generalization to unseen initial critical dimensions and encouraging initial transferability to preprocessed experimental SEM images, suggesting its potential as an efficient surrogate for TCAD-assisted process development while maintaining high geometric fidelity.

Micromachines doi: 10.3390/mi17050545

Authors: Claudia Cirillo Mariagrazia Iuliano Nicola Funicello Salvatore De Pasquale Maria Sarno

The rapid and reliable detection of dopamine (DA) is crucial for clinical diagnostics and neurochemical research. Here, we present an advanced electrochemical sensor fabricated by integrating 3D printing technology with bimetallic nanomaterials to achieve high sensitivity, selectivity, and reproducibility. A conductive polylactic acid (PLA) electrode was 3D-printed and subsequently activated to expose electroactive carbon domains. The surface was then modified with AgPt bimetallic nanoparticles (NPs), synthesized via a one-step solvothermal method, and coated with NafionTM 117 to form the AgPt@A-3DPE sensor platform. Morphological and structural characterization confirmed the formation of uniform, quasi-spherical AgPt nanoparticles with excellent dispersion. The sensor exhibited outstanding electrochemical performance, including a wide linear detection range for DA (0.5–100 µM), a low limit of detection (LOD) of 0.037 µM, and a significantly enhanced electroactive surface area (1.04 cm2). Furthermore, it demonstrates high selectivity in complex matrices, with minimal interference from common biomolecules such as ascorbic acid, uric acid, and glucose. Moreover, the practical applicability of the AgPt@A-3DPE sensor was successfully validated through the analysis of real human urine samples. This work demonstrates a low-cost, scalable, and highly efficient sensing approach, opening new avenues for personalized diagnostics and real-time monitoring of neurotransmitters in biomedical applications.

Micromachines doi: 10.3390/mi17050544

Authors: Huanqing Chen Menglai Lei Linghai Meng Zihao Chu Weihua Chen Xiaodong Hu

In this work, we report the realization of curved distributed Bragg reflectors (DBRs) without the need for lithography to achieve strong lateral confinement in a GaN-based vertical cavity. By embedding SiO2 nanospheres during deposition, curved DBRs with a funnel-shaped cross-section were fabricated. Based on the formed curved DBRs, a vertical cavity with a quality factor exceeding 2800 and a mode volume below 0.14 μm3 was successfully fabricated. The optical pumping threshold power of a vertical cavity surface-emitting laser (VCSEL) with a curved DBR was reduced to 76 nW, which is one order of magnitude lower than that of the same VCSEL with double-planar DBRs. Near-field patterns revealed that the curved-DBR VCSEL emits a circularly symmetric TEM00 mode with a full width at half maximum (FWHM) of only 1.8 μm. We believe this is an effective technique for fabricating low-threshold or small-aperture VCSELs.

Micromachines doi: 10.3390/mi17050543

Authors: Felipe Lucena Souza Medeiros Alexandre Jean René Serres Georgina Karla de Freitas Serres Ravania Luciano Martildes Caio Vasconcelos Benigno de Abrantes

This work presents a loop-shaped (hairpin) resonator incorporating a defective ground structure (DGS) to enhance sensitivity for monitoring water–glucose solutions. The proposed sensor exhibits two resonant frequencies at 2.61 GHz and 4.07 GHz, with reflection coefficients of −46.60 dB and −23.00 dB, respectively. A set of measurements was conducted to compare the performance of the resonator with and without the DGS under two sample-placement configurations: one with water and water–glucose solutions positioned over the feed lines and metallic resonant elements, and another with the water–glucose solutions placed directly over the ground plane. Among the evaluated cases, the ground-plane configuration proved to be the most advantageous, as it produced no frequency shift while yielding distinct magnitude responses of −41.91 dB, −45.62 dB, −47.74 dB, and −49.69 dB for glucose concentrations of 100, 150, 200, and 250 mg/dL, respectively. Overall, the resonator with the defective ground structure consistently demonstrated higher sensitivity and a more stable response pattern, indicating its strong potential for glucose-level monitoring applications.

Micromachines doi: 10.3390/mi17050542

Authors: Yuanhu Gu Jiansheng Liu Zhangping You Longfei Wu Hao Chen

This paper presents a case study demonstrating the use of the moving least square method (MLS) for modeling the mechanical response of an electrothermal microactuator. Under the MLS framework, the governing equations for heat transfer and structural mechanics are discretized across the computational domain. The resulting discrete electrothermal system is solved accurately through an incremental load and Newton–Raphson iterative method to determine the temperature field. Subsequently, the displacement field is obtained by solving the discrete mechanical equation, which includes contributions from natural boundary conditions. Convergence of the temperature solution is rigorously evaluated across different iterative schemes. The accuracy of the MLS solutions is validated against experimental temperature data and finite element method (FEM) simulations. Results indicate that the temperature distribution obtained from the MLS aligns well with both experimental and FEM results, even under idealized boundary conditions. Additionally, a similarly favorable comparison is observed between the displacement fields predicted by the MLS, polynomial point interpolation collocation method (PPCM), and FEM.

Micromachines doi: 10.3390/mi17050541

Authors: Victor Akpe Ian E. Cock

This review evaluates recent progress in nanozyme-based biosensors for detecting circulating tumour cells, nucleic acids, and protein biomarkers, with particular attention to how peroxidase-, oxidase-, and catalase-like reactions enhance signal generation across electrochemical, optical, and microfluidic platforms. The roles of iron oxide–gold composites, silica nanostructures, quantum dots, and hybrid nanomaterials in improving analytical performance, enabling multiplexed detection, and facilitating assay miniaturization are critically assessed. Advances such as amplification-free detection approaches, smartphone-compatible point-of-care systems, and AI-assisted data analysis are discussed in relation to their translational potential. Key barriers, including regulatory requirements, reproducibility concerns, and manufacturing scalability, are also evaluated. By integrating mechanistic understanding with practical considerations for clinical deployment, this review outlines how next-generation nanozyme-based biosensors may strengthen early cancer detection, real-time monitoring, and precision oncology.

Micromachines doi: 10.3390/mi17050540

Authors: Faisal bin Nasser Sarbaland Masashi Kobayashi Daiki Tanaka Risa Fujita Nobuyuki Tanaka Masahiro Furuya

Laminar co-flow in microchannels typically results in stratified streams with diffusion-limited mixing. This work presents an additively manufactured microfluidic platform that integrates a pulse tank and a transverse injection nozzle into an otherwise straight channel, enabling pulse-driven mixing and droplet generation using air-pressure actuation alone. In Device A, transverse pulsed injection disrupted the stratified interface and significantly enhanced mixing compared with the no-pulse case, as confirmed by an entropy-based mixing index. In Device B, pulsed injection into a continuous oil phase enabled stable droplet-on-demand generation with pressure-tunable droplet diameter in a straight circular channel. The devices operated in a laminar regime, with representative Reynolds, Péclet, and capillary numbers confirming diffusion-limited baseline mixing and stable dripping-type droplet formation. The results demonstrate that pulse-driven injections in a simple, additively manufactured geometry provide an effective, low-complexity approach to mixing enhancement and droplet generation without external fields or complex channel designs.

Micromachines doi: 10.3390/mi17050539

Authors: Yijun Yang Dong Geon Jung Daewoong Jung

This work presents the design and evaluation of cerium and zinc oxide-incorporated indium oxide (Ce/ZnO-In2O3) nanocube composites synthesized via a hydrothermal process for advanced ethanol gas sensing. The incorporation of Ce and ZnO effectively modified the surface chemistry and electronic structure of In2O3 without causing significant morphological degradation. Compared with pristine In2O3, the Ce/ZnO-In2O3 sensor exhibited a significantly enhanced response of 33.2 toward 100 ppm ethanol at 300 °C, corresponding to an 8.7-fold improvement, along with a low detection limit of 0.8 ppm. In addition, the composite sensor demonstrated stable and reversible sensing behavior, excellent repeatability over 100 cycles, and long-term operational stability. Notably, improved humidity tolerance was achieved, with approximately 77% of the initial response retained at 80% relative humidity. The enhanced sensing performance is attributed to the combined effects of heterojunction formation between ZnO and In2O3 and Ce-induced lattice distortion, which promote oxygen adsorption and facilitate charge transfer during gas reactions. Principal component analysis (PCA) further confirmed the improved discrimination of ethanol against interfering gases. These results underscore the synergistic effects of Ce and ZnO incorporation in tailoring electronic structures and surface chemistry, thereby emphasizing the potential of this strategy for reliable ethanol detection in environmental and industrial applications.

Micromachines doi: 10.3390/mi17050538

Authors: Sebastian Zapata Brady Goenner Dallin S. Miner Bruce K. Gale Gregory P. Nordin

Post-processing remains a major bottleneck in the fabrication of microfluidic devices using Digital Light Processing Stereolithography (DLP-SLA) 3D printing, where unpolymerized resin trapped within internal structures must be removed without damaging delicate features such as thin membranes, valves, and pumps. Manual flushing is slow, inconsistent, and prone to structural failure, especially as device complexity and port counts increase. Here, we present the first fully automated flushing system for DLP-SLA microfluidic devices, enabled by a standardized chip-to-chip (C2C) interconnect architecture and an electronically controlled pneumatic routing platform. A reusable 32-port flushing interface chip provides alignment, sealing, and modular coupling to arbitrary device chips through integrated microgaskets, while a network of electronic pressure controllers, differential pressure sensors, and multi-port rotary valves enable precise, programmable application of pressure, vacuum, and solvent conditions. We introduce a fluidic-circuit model of the system that relates applied pressure to the pressure drop across device structures and experimentally validate this model using channels with varying fluidic resistances. Using this platform, we demonstrate robust flushing of both passive (straight and serpentine channels) and active (valves, pumps) microfluidic elements, as well as application-specific devices including mixers and concentration-gradient generators. Our system eliminates manual handling, improves valve membrane survival, and provides repeatable flushing across a broad range of device geometries. This work establishes a scalable foundation for automated post-processing in 3D-printed microfluidics and significantly advances the practicality of DLP-SLA fabrication for complex, multi-layered microfluidic devices.

Micromachines doi: 10.3390/mi17050537

Authors: Akeel Qadir Fayyaz Muhammad Shahid Karim Jinkai Chen Hongsheng Xu Umar Farooq

Surface Acoustic Wave (SAW) magnetic sensors are traditionally fabricated on rigid substrates, which severely limits their application on curved or irregular surfaces. To address this critical limitation, this paper presents a novel flexible SAW magnetic sensor based on a grating-arrayed Terfenol-D thin film deposited on a 50 µm thick flexible lithium niobate (LiNbO3) substrate. Unlike conventional designs using a continuous magnetostrictive layer, the proposed grating-arrayed structure is designed to aid in hysteresis compensation and minimize measurement errors associated with residual magnetization. As demonstrated experimentally, the sensors achieve a high sensitivity of 85.8 kHz/mT for devices with λ-wide gratings and a maximum frequency shift of 377 kHz at 5 mT. A systematic investigation reveals that sensitivity is critically dependent on the grating width and film thickness, with 500 nm thick gratings yielding optimal performance. Crucially, the sensor’s functionality under mechanical deformation is validated, and a differential measurement method is introduced to effectively compensate for stress-induced frequency shifts, ensuring reliable operation in practical, non-ideal conditions. The results confirm the sensor’s robust performance under the tested stress conditions, positioning this flexible SAW magnetic sensor as a promising solution for advanced, conformable sensing applications.

Micromachines doi: 10.3390/mi17050536

Authors: Xiaojun Tan Xuyun Peng Wei Tan Jian Huang Chaojun Ding Yushan Yang Jieshun Yang Haitao Chen Liang Guo Qingmao Zhang

With the strategic shift toward reducing reliance on critical raw materials, Cobalt-free eutectic high-entropy alloys (EHEAs) have emerged as a pivotal frontier for high-performance structural applications. This review systematically elucidates the synergistic relationship between Co-free alloy design and the non-equilibrium solidification mechanisms of Selective Laser Melting (SLM). The ultra-high cooling rates (105–108 K/s) inherent in SLM are shown to refine eutectic lamellae to the sub-micron scale (typically <300 nm), effectively suppressing the macro-segregation common in conventional casting. We evaluate the design principles of Al-Cr-Fe-Ni and related systems, noting that SLM-processed Co-free EHEAs frequently achieve yield strengths exceeding 1000 MPa and ultimate tensile strengths (UTSs) surpassing 1300 MPa, while maintaining tensile elongations above 10%—a significant improvement over the coarse-grained structures produced by traditional methods. Furthermore, the study identifies critical processing windows, such as laser energy densities (60–120 J/mm3), required to mitigate micro-cracking and achieve near-full density (>99.5%). By synthesizing recent experimental breakthroughs and AI-driven modeling, this review provides a quantitative roadmap for the precision manufacturing of cost-effective, high-performance EHEAs, bridging the gap between theoretical alloy design and industrial additive manufacturing.

Micromachines doi: 10.3390/mi17050535

Authors: Huan Wang Shu Yang Zhen Chen Haoyu Sun Yang Shen Hang Li Zhiyu Jiang Yanlei Li Xingdong Liang

Lightweight Unmanned Aerial Vehicles (UAVs) have limited space, low payload capacity, and constrained power supply capabilities. Therefore, their payloads are constrained by size, weight, and power (SWaP). Thus, designing edge-side signal processing architectures for the payloads of UAVs faces severe challenges. Traditional ASIC design based on manual optimization struggles to meet the demands of low latency and low resource occupancy in edge-side applications. To address this challenge, this paper proposes a signal processing hardware accelerator architecture design framework with algorithm-hardware co-design. The framework employs a cross-level dataflow graph representation to formally capture task characteristics. Reconfigurable dataflow templates and reusable operator IP components are systematically constructed based on this representation. Through multi-objective design space exploration, the framework achieves Pareto-optimal mapping from algorithmic specifications to hardware implementations. Finally, automatic generation of top-level hardware descriptions enables rapid FPGA-based prototyping and functional validation. Taking synthetic aperture radar (SAR) imaging as a study example, compared with non-reconfigurable architectures, this scheme reduces the equivalent gate count by 51.4% without increasing processing latency. Compared with a conventional reconfigurable dataflow architecture, the design improves energy efficiency from 12.8 MS/J to 16.0 MS/J, representing a 25.4% enhancement, while also scaling the supported data processing size by a factor of 4×. It provides a high-performance and scalable hardware acceleration solution for lightweight edge-side computing platforms.

Micromachines doi: 10.3390/mi17050533

Authors: Alexander V. Andrianov Alexey A. Shakhmin Alexey G. Petrov Nikolay V. Sivov Grigory I. Kropotov

Chalcogenide glasses are known as optical materials for the infrared spectral range. These compounds may also be of interest as materials for the low-frequency part of the terahertz range of electromagnetic waves, which is currently being intensively studied in connection with the numerous possible applications of terahertz radiation. However, the terahertz optical characteristics of chalcogenide glasses remain poorly studied. In this work, eight different compositions of GeAsSeSbSnTe chalcogenide glasses were investigated using terahertz time-domain spectroscopy. A number of compositions, in particular GeSeTe and AsSeSbSn, were studied in the terahertz spectral range for the first time. Spectra of the refractive index and extinction coefficient were obtained for studied materials in the spectral range of 0.1–2.2 THz. The experimental frequency dependence of the product of the terahertz power absorption coefficient and the refractive index for the entire set of studied glasses is approximated by a power function. It was established that the exponent of the approximating power functions varies from 1.68 to 2.34 depending on the composition of the chalcogenide glass. For the studied glasses, a correlation was found between the values of the average coordination number characterizing the chalcogenide glass structure, and the values of the exponent of the functions approximating the THz absorption spectra.

Micromachines doi: 10.3390/mi17050534

Authors: Hyunwoo Koo Horim Lee Kyounghwan Kim Eiyong Park Yongjun Kim Sung-Hoon Hong Sang-Bok Lee Sungjoon Lim

In this study, we propose a novel approach to enhance upper stop-band attenuation in a split-ring resonator-based bandpass filter by partially inserting W-type hexaferrite films into a strategically placed mechanical hole. The hexaferrite exhibits a substantial increase in magnetic loss tangent in the desired band owing to ferromagnetic resonance, considerably improving attenuation in the upper stop-band while maintaining an acceptable insertion loss in the pass-band. The obtained results indicate that selectively placing the hexaferrite film enhances out-of-band rejection by up to 4 dB, with a slight degradation of 0.84 dB in pass-band insertion loss. Before inserting the hexaferrite film, the bandpass filter exhibited an insertion loss of 1.01 dB at 28 GHz and an attenuation of 20.04 dB at 32 GHz. By contrast, after inserting the hexaferrite film, the bandpass filter exhibited an insertion loss of 1.95 dB at 28 GHz and an attenuation of 24.45 dB at 32 GHz.

Micromachines doi: 10.3390/mi17050532

Authors: Adriano Colombelli Daniela Lospinoso Vita Guarino Alessandra Zizzari Monica Bianco Valentina Arima Roberto Rella Maria Grazia Manera

Rapid sterility testing of radiopharmaceuticals is essential due to their short half-lives and strict safety requirements. Conventional culture-based methods require several days and are not compatible with clinical workflows. In this work, we present a proof-of-concept droplet-based microfluidic platform for rapid optical detection of bacterial contamination through optical extinction analysis of microdroplets. Monodisperse water-in-oil microdroplets were generated and optically interrogated using a fiber-based detection system. Calibration was first performed using 500 nm polystyrene nanoparticles to establish the relationship between particle concentration and optical extinction. Subsequently, Staphylococcus aureus suspensions were analyzed under aerobic and anaerobic conditions at concentrations ranging from 0 to 230 CFU/mL. The system demonstrated reliable detection of bacterial contamination with estimated limits of detection of ~15 CFU/mL (aerobic) and ~7.5 CFU/mL (anaerobic). The platform enables real-time, high-throughput analysis with minimal sample handling and reduced analysis time compared to conventional sterility tests. This study validates the feasibility of microdroplet-based optical detection as a rapid quality control strategy specifically suited for radiopharmaceutical production, where the short half-lives of common radiotracers impose strict time constraints incompatible with conventional 14-day culture-based sterility tests. The results provide a proof-of-concept foundation for future integration into automated sterility testing workflows, with further validation on real radiopharmaceutical matrices planned as the next step.

Micromachines doi: 10.3390/mi17050531

Authors: Yuguo Li Shuo Tian Wenzheng Sun Longfa Chen Jian Li Junkai Hu Na Meng

A high-precision and efficient surface defect detection for printed circuit board (PCB) is critical to ensuring the reliability of electronic systems. However, the presence of complex circuit backgrounds and the small scale of defects often limit the precision and effectiveness of conventional inspection approaches. To address these challenges, this paper proposes FMW-YOLO, a lightweight and accurate detection framework based on YOLO11n. Specifically, a Frequency-Enhanced Channel-Transposed and Local Feature backbone network is developed to improve feature extraction. By designing a Dual-Frequency and Channel Attention Aggregation module and a Lightweight Edge-Gaussian Block, the original C3k2 structure is refined to suppress noise interference while preserving high-frequency details, thereby enhancing feature representation. Furthermore, a neck network incorporating a Multi-Scale Context-Aware Enhancement mechanism is constructed, in which an Attention-Integrated Feature Pyramid is employed to facilitate more effective cross-scale feature interaction. In addition, a Dilated Reparam Residual Module is embedded into the C3k2 structure to expand the receptive field without significantly increasing computational burden. Finally, Wise-IoU is adopted to optimize bounding box regression by assigning greater importance to anchors of moderate quality. Extensive experiments conducted on the HRIPCB and DeepPCB datasets demonstrate that FMW-YOLO improves mAP50 by 2.1% and 0.3%, respectively, while reducing the number of parameters by 23%. These results indicate that the proposed method achieves improved detection accuracy and demonstrates strong potential for practical industrial applications.

Micromachines doi: 10.3390/mi17050530

Authors: Huiyuan Zhang Pengfei Jia Ming Nie Jiayun Zhu Zhiyuan Li

With the proposal of transparent power grids, advanced sensor research has become a hot topic. A partial discharge (PD) sensor is a specialized device that captures electrical signals generated by partial discharge phenomena in power system insulation, enabling real-time monitoring of insulation status and early warning of potential faults. However, the detection sensitivity and signal transmission efficiency of conventional PD sensors are constrained by the intrinsic properties of their sensing materials. This paper focuses on the improvement of the PD sensor using advanced graphene sensing materials. First-principles calculations were performed to evaluate the key charge parameters of the PD sensor. The microstructure model of the PD sensor is constructed, and the charge parameter properties of the graphene partial discharge sensor are calculated and revealed under simulated electric field. Then, the charge transport characteristics of the PD sensor are simulated. The results reveal that the graphene-based sensor exhibits a significantly enhanced transport coefficient—approximately 66% higher than that of conventional sensor materials. Subsequent experiments revealed the better signal transmission of the graphene PD sensor, which outperformed the traditional sensor by 40%. This study provides a microscopic theoretical reference for optimizing electrode plate materials from the atomic level and the device level, which is of great significance for the design and development of high-performance PD sensor power grids.