Micromachines

23 pages, 2881 KiB

Open AccessArticle

Nondestructive Mechanical and Electrical Characterization of Piezoelectric Zinc Oxide Nanowires for Energy Harvesting

by Frank Eric Boye Anang, Markys Cain, Min Xu, Zhi Li, Uwe Brand, Darshit Jangid, Sebastian Seibert, Chris Schwalb and Erwin Peiner

Micromachines 2025, 16(8), 927; https://doi.org/10.3390/mi16080927 (registering DOI) - 12 Aug 2025

Abstract

In this study we report on the structural, mechanical, and electrical characterization of different structures of vertically aligned zinc oxide (ZnO) nanowires (NWs) synthesized using hydrothermal methods. By optimizing the growth conditions, scanning electron microscopy (SEM) micrographs show that the ZnO NWs could [...] Read more.

In this study we report on the structural, mechanical, and electrical characterization of different structures of vertically aligned zinc oxide (ZnO) nanowires (NWs) synthesized using hydrothermal methods. By optimizing the growth conditions, scanning electron microscopy (SEM) micrographs show that the ZnO NWs could reach an astounding 51.9 ± 0.82 µm in length, 0.7 ± 0.08 µm in diameter, and 3.3 ± 2.1 µm^-2 density of the number of NWs per area within 24 h of growth time, compared with a reported value of ~26.8 µm in length for the same period. The indentation modulus of the as-grown ZnO NWs was determined using contact resonance (CR) measurements using atomic force microscopy (AFM). An indentation modulus of 122.2 ± 2.3 GPa for the NW array sample with an average diameter of ~690 nm was found to be close to the reference bulk ZnO value of 125 GPa. Furthermore, the measurement of the piezoelectric coefficient (d₃₃) using the traceable ESPY33 tool under cyclic compressive stress gave a value of 1.6 ± 0.4 pC/N at 0.02 N with ZnO NWs of 100 ± 10 nm and 2.69 ± 0.05 µm in diameter and length, respectively, which were embedded in an S1818 polymer. Current–voltage (I-V) measurements of the ZnO NWs fabricated on an n-type silicon (Si) substrate utilizing a micromanipulator integrated with a tungsten (W) probe exhibits Ohmic behavior, revealing an important phenomenon which can be attributed to the generated electric field by the tungsten probe, dielectric residue, or conductive material. Full article

(This article belongs to the Special Issue Research Progress on Advanced Piezoelectric Energy Harvesters)

16 pages, 1652 KiB

Open AccessArticle

Cell Partitioning Design for Microfluidic ATPS Devices: A Dynamic Energy Strategy and Calculation Using Chondrocytes and Model Microparticles

by Gabriel Garibaldi, Jimena Alegria, Anita Shayan, Robert Stannert, Nehal I. Abu-Lail and Gongchen Sun

Micromachines 2025, 16(8), 926; https://doi.org/10.3390/mi16080926 (registering DOI) - 12 Aug 2025

Abstract

Sorting and isolating specific cells from heterogeneous populations are crucial for many biomedical applications, including drug discovery and medical diagnostics. Conventional methods such as Fluorescent Activated Cell Sorting (FACS) and Magnetic Activated Cell Sorting (MACS) face limitations in throughput, cost, and the ability [...] Read more.

Sorting and isolating specific cells from heterogeneous populations are crucial for many biomedical applications, including drug discovery and medical diagnostics. Conventional methods such as Fluorescent Activated Cell Sorting (FACS) and Magnetic Activated Cell Sorting (MACS) face limitations in throughput, cost, and the ability to separate subtly different cells. Cell partitioning in Aqueous Two-Phase Systems (ATPSs) offers a biocompatible and cost-effective alternative, particularly when combined with continuous-flow microfluidics. However, it remains challenging to rationally design microfluidic ATPS devices and operation to separate cells with similar origin but different phenotypes. In this paper, using a model ATPS, polyethylene glycol (PEG)—Dextran (Dex) system, and model cells, human chondrocytes (hChs), and carboxylated polystyrene (PS) microparticles, we systematically characterized the material properties affecting cell partitioning in ATPSs, such as surface energies of the solutions and cells and solution viscosities. We developed an energy balance approach between interfacial energy and viscous dissipation to estimate the interface translocation dynamic of cells partitioning into the preferred phase. Combining the experimental measurement and the energy balance model, our calculation reveals that the time required for complete cell partitioning at the ATPS interface can be exploited in microfluidic ATPS devices to separate hChs with different phenotypes (healthy and diseased). We expect our dynamic energy approach to provide a basis and a design strategy for optimizing microfluidic ATPS devices to achieve the efficient separation of phenotypically similar cell populations and further expand the potential of microfluidic cell separation. Full article

(This article belongs to the Special Issue Micro/Nanotechnology for Cell Manipulation, Detection and Analysis)

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13 pages, 4450 KiB

Open AccessArticle

Laser-Based Selective Removal of EMI Shielding Layers in System-in-Package (SiP) Modules

by Xuan-Bach Le, Won Yong Choi, Keejun Han and Sung-Hoon Choa

Micromachines 2025, 16(8), 925; https://doi.org/10.3390/mi16080925 - 11 Aug 2025

Abstract

With the increasing complexity and integration density of System-in-Package (SiP) technologies, the demand for selective electromagnetic interference (EMI) shielding is growing. Conventional sputtering processes, while effective for conformal EMI shielding, lack selectivity and often require additional masking or post-processing steps. In this study, [...] Read more.

With the increasing complexity and integration density of System-in-Package (SiP) technologies, the demand for selective electromagnetic interference (EMI) shielding is growing. Conventional sputtering processes, while effective for conformal EMI shielding, lack selectivity and often require additional masking or post-processing steps. In this study, we propose a novel, laser-based approach for the selective removal of EMI shielding layers without physical masking. Numerical simulations were conducted to investigate the thermal and mechanical behavior of multilayer EMI shielding structures under two irradiation modes: full-area and laser scanning. The results showed that the laser scanning method induced higher interfacial shear stress, reaching up to 38.6 MPa, compared to full-area irradiation (12.5 MPa), effectively promoting delamination while maintaining the integrity of the underlying epoxy mold compound (EMC). Experimental validation using a nanosecond pulsed fiber laser confirmed that complete removal of the EMI shielding layer could be achieved at optimized laser powers (~6 W) without damaging the EMC, whereas excessive power (8 W) caused material degradation. The laser scanning speed was 50 mm/s, and the total laser irradiation time of the package was 0.14 s, which was very fast. This study demonstrates the feasibility of a non-contact, damage-free, and selective EMI shielding removal technique, offering a promising solution for next-generation semiconductor packaging. Full article

(This article belongs to the Special Issue Emerging Packaging and Interconnection Technology, Second Edition)

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11 pages, 8091 KiB

Open AccessArticle

Wireless Communication Using a Radiation-Type Metasurface

by Jun Chen Ke, Li Wang, Mingzhu Jiang and Qiang Wang

Micromachines 2025, 16(8), 924; https://doi.org/10.3390/mi16080924 - 11 Aug 2025

Abstract

The rapid development of metasurfaces offers new possibilities to establish novel wireless communication systems with simplified architectures. However, the current demonstration systems are based on the reflection-type metasurfaces, which suffer from high profiles and integration challenges in practice. Such configurations are also inefficient [...] Read more.

The rapid development of metasurfaces offers new possibilities to establish novel wireless communication systems with simplified architectures. However, the current demonstration systems are based on the reflection-type metasurfaces, which suffer from high profiles and integration challenges in practice. Such configurations are also inefficient for handling multiple subcarriers during beam scanning and beam tracking. To address these limitations, a radiation-type metasurface fed by a microstrip array antenna is proposed in this paper, which is used to construct a new-architecture wireless communication system. Compared to the reported metasurface-based communication systems, the proposed design is more flexible for information modulation and transmission, with the system profile significantly reduced. The phase modulation is implemented by changing the transmission phase of metasurface, allowing for baseband signals to be directly imparted to the carrier wave from the feeding source. A real-time signal transmission experiment validates the performance of the proposed metasurface-based communication system. Full article

(This article belongs to the Special Issue Electromagnetic Metamaterials and Metasurfaces: From Design to Applications)

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17 pages, 3231 KiB

Open AccessArticle

Research on Cutting Force Modeling and Machining Performance of Discrete-Edge End Mill

by Ming Song, Minli Zheng, Siyuan Gao, Baojuan Dong and Jianping Zhu

Micromachines 2025, 16(8), 923; https://doi.org/10.3390/mi16080923 - 10 Aug 2025

Viewed by 113

Abstract

To address the challenges of complex cutting force formation and low prediction accuracy in discrete-edge end mills, this study proposes a precise cutting force modeling method based on an effective chip slot function. An effective chip slot function is established to quantitatively characterize [...] Read more.

To address the challenges of complex cutting force formation and low prediction accuracy in discrete-edge end mills, this study proposes a precise cutting force modeling method based on an effective chip slot function. An effective chip slot function is established to quantitatively characterize the dynamic variation of cutting edge engagement along different axial positions. Based on the instantaneous uncut chip thickness theory by Altintas, a high-precision cutting force model suitable for discrete-edge tools is developed. Experimental results show that the proposed model achieves an average prediction error of 4.82%, with a maximum error below 10%, demonstrating its high accuracy and practical applicability. Comparative experiments with conventional continuous-edge end mills under identical machining conditions indicate that the discrete-edge tool can reduce cutting forces (F_x by 7.2%, F_y by 3.2%), significantly suppress cutting vibrations (fluctuation coefficients reduced by 13.5% and 21.9%, respectively), and lower surface roughness to approximately one-sixth of that produced by conventional tools. The results confirm that discrete-edge end mills exhibit notable advantages in machining stability, cutting force control, and surface quality, providing a solid theoretical foundation for the design and process optimization of high-performance cutting tools. Full article

(This article belongs to the Special Issue Advanced Manufacturing Technology and Systems, 3rd Edition)

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17 pages, 9812 KiB

Open AccessArticle

Study on the Influence of Deformation and Temperature on the Properties of High-Strength Tungsten Alloy Wire

by Junling Fan, Jingwen Du, Jun Cao, Yongzhen Sun and Junchao Zhang

Micromachines 2025, 16(8), 922; https://doi.org/10.3390/mi16080922 - 10 Aug 2025

Viewed by 117

Abstract

In this paper, high-strength W-1%La₂O₃ alloy wire was obtained by solid-state doping using tungsten powder and lanthanum oxide, large deformation rotary forging and wire drawing, which solved the disadvantages of traditional tungsten alloy wire processing such as the uneven distribution [...] Read more.

In this paper, high-strength W-1%La₂O₃ alloy wire was obtained by solid-state doping using tungsten powder and lanthanum oxide, large deformation rotary forging and wire drawing, which solved the disadvantages of traditional tungsten alloy wire processing such as the uneven distribution of rare earth oxides. The effects of rotary forging and annealing on the microstructure and properties of tungsten alloy were studied, which provided some basis for preparing high-strength tungsten alloy wire. The results indicate that tungsten alloy undergoes recovery at relative high temperatures (1480–1380 °C) during the rotary forging process. After large deformation, subgrains and uneven microstructures appear, so annealing is required before tungsten alloys wire drawing processing. With increasing annealing temperature, the recrystallization degree gradually increases and the hardness of tungsten alloy gradually decreases. When the deformation is less than 81.2%, tungsten alloy wire exhibits brittle fracture. When the deformation increases to 88.4% (ø0.8 mm), the fracture surface of the wire exhibits a plastic–brittle mixed fracture mechanism. Full article

(This article belongs to the Special Issue Ultra-Precision Machining of Difficult-to-Machine Materials—Second Edition)

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11 pages, 1580 KiB

Open AccessArticle

Research on a Graded Self-Powered Vibration Sensor for Geological Drilling

by Jingui Zhang and Chuan Wu

Micromachines 2025, 16(8), 921; https://doi.org/10.3390/mi16080921 - 10 Aug 2025

Viewed by 131

Abstract

Downhole vibration measurement is a key link for optimizing drilling parameters and ensuring operational safety; however, powering conventional vibration sensors reduces drilling efficiency and increases drilling costs. This paper introduces a triboelectric nanogenerator-based, graded, and self-powered vibration sensor designed for geological drilling, enabling [...] Read more.

Downhole vibration measurement is a key link for optimizing drilling parameters and ensuring operational safety; however, powering conventional vibration sensors reduces drilling efficiency and increases drilling costs. This paper introduces a triboelectric nanogenerator-based, graded, and self-powered vibration sensor designed for geological drilling, enabling the concurrent measurement of vibration frequency and amplitude. Experimental results show that the sensor has a measurement range for vibration frequency from 0 Hz to 11 Hz and can measure amplitude thresholds of 10 mm, 25 mm, 40 mm, and 55 mm. The measurement errors for both vibration frequency and amplitude are less than 3%, and it can operate stably under conditions of temperature below 150 °C and humidity below 90%, demonstrating good environmental adaptability. Furthermore, the sensor has self-powering capabilities, with a maximum output voltage reaching 11.8 V, a peak current of 28 nA, and a peak output power of 4 × 10⁻⁷ W into an external resistance of 6 × 10⁷ Ω. In contrast to conventional downhole vibration sensors, this device integrates self-powering with graded amplitude detection, enhancing its suitability for real-world drilling applications. Full article

(This article belongs to the Special Issue Micro/Nanostructures in Sensors and Actuators, 2nd Edition)

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18 pages, 4583 KiB

Open AccessArticle

Bright Blue Light Emission of ZnCl₂-Doped CsPbCl₁Br₂ Perovskite Nanocrystals with High Photoluminescence Quantum Yield

by Bo Feng, Youbin Fang, Jin Wang, Xi Yuan, Jihui Lang, Jian Cao, Jie Hua and Xiaotian Yang

Micromachines 2025, 16(8), 920; https://doi.org/10.3390/mi16080920 - 9 Aug 2025

Viewed by 191

Abstract

The future development of perovskite light-emitting diodes (LEDs) is significantly limited by the poor stability and low brightness of the pure-blue emission in the wavelength range of 460–470 nm. In this study, the Cl/Br element ratio in CsPbCl_xBr_3−x perovskite nanocrystals [...] Read more.

The future development of perovskite light-emitting diodes (LEDs) is significantly limited by the poor stability and low brightness of the pure-blue emission in the wavelength range of 460–470 nm. In this study, the Cl/Br element ratio in CsPbCl_xBr_3−x perovskite nanocrystals (NCs) was modulated to precisely control their blue emission in the 428–512 nm spectral region. Then, the undoped CsPbCl₁Br₂ and the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs were synthesized via the hot-injection method and investigated using variable-temperature photoluminescence (PL) spectroscopy. The PL emission peak of the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs exhibits a blue shift from 475 nm to 460 nm with increasing ZnCl₂ doping concentration. Additionally, the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs show a high photoluminescence quantum yield (PLQY). The variable-temperature PL spectroscopy results show that the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs have a larger exciton binding energy than the CsPbCl₁Br₂ perovskite NCs, which is indicative of a potentially higher PL intensity. To assess the stability of the perovskite NCs, high-temperature experiments and ultraviolet-irradiation experiments were conducted. The results indicate that zinc doping is beneficial for improving the stability of the perovskite NCs. The ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs were post-treated using didodecylammonium bromide, and after the post-treatment, the PLQY increased to 83%. This is a high PLQY value for perovskite NC-LEDs in the blue spectral range, and it satisfies the requirements of practical display applications. This work thus provides a simple preparation method for pure blue light-emitting materials. Full article

(This article belongs to the Special Issue Advanced Optoelectronic Materials/Devices and Their Applications)

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22 pages, 11628 KiB

Open AccessArticle

Study of the Sensitivity of DC Arc Temperature Field, Pressure Field, and Potential to Process Parameters

by Yongjun Liu, Gaosong Li, Shuai Zhang and Zhenya Wang

Micromachines 2025, 16(8), 919; https://doi.org/10.3390/mi16080919 - 9 Aug 2025

Viewed by 85

Abstract

DC arcs are widely used in many fields such as shipbuilding, machinery manufacturing, and aerospace due to their advantages of high energy density, simple structure, and low price. However, there are few studies on the sensitivity of the arc pressure and temperature fields [...] Read more.

DC arcs are widely used in many fields such as shipbuilding, machinery manufacturing, and aerospace due to their advantages of high energy density, simple structure, and low price. However, there are few studies on the sensitivity of the arc pressure and temperature fields to current and protective gas flow rate. In order to solve this problem, this paper establishes a numerical model for the coupling of DC arc electric–thermal–flow multi-physical fields. Based on this model, the variation rules of the arc temperature, pressure, and potential field with current or protective gas flow rate are studied, respectively, when the current is 100–600 A or the gas flow rate is 18–48 L/min. The results show that the current is the most important factor in the sensitivity of the arc temperature and potential field to the current and protective gas flow rate. With the increase in current, the Joule heat power increases significantly, and the arc central temperature shows a nonlinear increase to 27,000 K. With increasing current, the peak of the pressure field gradually shifts to the region below the top of the wire arc, and the highest pressure increases by 14 times. When the current is small, the increase in argon flow rate can inhibit the spreading of the temperature field by forced convection; when the current is large, the arc contraction with an increasing argon flow rate leads to an anomalous increase in the arc-central temperature. In addition, the energy accumulation mechanism in the strong-current–high-flow-rate coupling region is also revealed, a coupled mathematical model of arc contraction and turbulent loss under the Lorentz force is constructed, and the thermodynamic properties of the arc under the coupling of multi-physical fields are elucidated. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies, 2nd Edition)

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36 pages, 8596 KiB

Open AccessReview

Microrheology: From Video Microscopy to Optical Tweezers

by Andrea Jannina Fernandez, Graham M. Gibson, Anna Rył and Manlio Tassieri

Micromachines 2025, 16(8), 918; https://doi.org/10.3390/mi16080918 - 8 Aug 2025

Viewed by 224

Abstract

Microrheology, a branch of rheology, focuses on studying the flow and deformation of matter at micron length scales, enabling the characterization of materials using minute sample volumes. This review article explores the principles and advancements of microrheology, covering a range of techniques that [...] Read more.

Microrheology, a branch of rheology, focuses on studying the flow and deformation of matter at micron length scales, enabling the characterization of materials using minute sample volumes. This review article explores the principles and advancements of microrheology, covering a range of techniques that infer the viscoelastic properties of soft materials from the motion of embedded tracer particles. Special emphasis is placed on methods employing optical tweezers, which have emerged as a powerful tool in both passive and active microrheology thanks to their exceptional force sensitivity and spatiotemporal resolution. The review also highlights complementary techniques such as video particle tracking, magnetic tweezers, dynamic light scattering, and atomic force microscopy. Applications across biology, materials science, and soft matter research are discussed, emphasizing the growing relevance of particle tracking microrheology and optical tweezers in probing microscale mechanics. Full article

(This article belongs to the Special Issue Microrheology with Optical Tweezers)

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13 pages, 6459 KiB

Open AccessArticle

Total Ionizing Dose Effect Simulation Modeling and Analysis for a DCAP Power Chip

by Xinfang Liao, Danyang Lei, Yanjun Fu, Yuchen Liu, Kangqi Huang, Yuan Wei, Yinghong Zuo, Yashi Ying, Yi Liu, Changqing Xu and Yintang Yang

Micromachines 2025, 16(8), 917; https://doi.org/10.3390/mi16080917 - 8 Aug 2025

Viewed by 118

Abstract

In this paper, a systematic study on performance degradation of a 0.18 μm BCD-process DCAP (Direct connection to the output CAPacitor) power chip under a total-dose radiation environment is carried out. The effects of total-dose radiation on the electrical characteristics of an MOS [...] Read more.

In this paper, a systematic study on performance degradation of a 0.18 μm BCD-process DCAP (Direct connection to the output CAPacitor) power chip under a total-dose radiation environment is carried out. The effects of total-dose radiation on the electrical characteristics of an MOS device are analyzed through device-level simulation. Based on the simulation results, a total-dose fault injection model is established and applied to a circuit-level simulation of the DCAP power chip. Our simulation modeling and analysis results show that total-dose radiation degrades output voltage accuracy and switching frequency, to which the bandgap reference circuit is identified as the most sensitive module. The findings presented in this paper provide theoretical support for total-dose radiation hardening designs for the DCAP power chip. Full article

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39 pages, 4438 KiB

Open AccessReview

Graphene-Based Gas Sensors: State-of-the-Art Developments for Gas Sensing Applications

by Aviraj M. Teli, Sagar M. Mane, Sonali A. Beknalkar, Rajneesh Kumar Mishra, Wookhee Jeon and Jae Cheol Shin

Micromachines 2025, 16(8), 916; https://doi.org/10.3390/mi16080916 - 8 Aug 2025

Viewed by 209

Abstract

Gas sensors based on graphene have gained considerable attention because of graphene’s remarkable properties, such as its extensive surface area, impressive electrical conductivity, and exceptional mechanical strength. This review critically analyzes recent developments in functionalization strategies designed to enhance the sensitivity, selectivity, and [...] Read more.

Gas sensors based on graphene have gained considerable attention because of graphene’s remarkable properties, such as its extensive surface area, impressive electrical conductivity, and exceptional mechanical strength. This review critically analyzes recent developments in functionalization strategies designed to enhance the sensitivity, selectivity, and stability of graphene-based sensors. It discusses various chemical, physical, and hybrid functionalization methods, illustrating how surface alterations affect graphene’s interaction with target gas molecules. The paper also investigates the fundamental sensing mechanisms, including charge transfer, carrier mobility modulation, and Schottky barrier modification, to provide a thorough understanding of sensor response characteristics. Additionally, it highlights emerging applications in environmental monitoring, healthcare diagnostics, and industrial safety, demonstrating the transformative potential of these sensors in real-world settings. Finally, the review addresses challenges concerning reproducibility, long-term stability, and large-scale production, while also offering future insights on utilizing innovative nanomaterials and artificial intelligence to advance the next generation of graphene-based gas sensing technologies. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for High-Performance Gas Sensors)

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17 pages, 4004 KiB

Open AccessArticle

Research on Switching Current Model of GaN HEMT Based on Neural Network

by Xiang Wang, Zhihui Zhao, Huikai Chen, Xueqi Sun, Shulong Wang and Guohao Zhang

Micromachines 2025, 16(8), 915; https://doi.org/10.3390/mi16080915 - 7 Aug 2025

Viewed by 231

Abstract

The switching characteristics of GaN HEMT devices exhibit a very complex dynamic nonlinear behavior and multi-physics coupling characteristics, and traditional switching current models based on physical mechanisms have significant limitations. This article adopts a hybrid architecture of convolutional neural network and long short-term [...] Read more.

The switching characteristics of GaN HEMT devices exhibit a very complex dynamic nonlinear behavior and multi-physics coupling characteristics, and traditional switching current models based on physical mechanisms have significant limitations. This article adopts a hybrid architecture of convolutional neural network and long short-term memory network (CNN-LSTM). In the 1D-CNN layer, the one-dimensional convolutional neural network can automatically learn and extract local transient features of time series data by sliding convolution operations on time series data through its convolution kernel, making these local transient features present a specific form in the local time window. In the double-layer LSTM layer, the neural network model captures the transient characteristics of switch current through the gating mechanism and state transfer. The hybrid architecture of the constructed model has significant advantages in accuracy, with metrics such as root mean square error (RMSE) and mean absolute error (MAE) significantly reduced, compared to traditional switch current models, solving the problem of insufficient accuracy in traditional models. The neural network model has good fitting performance at both room and high temperatures, with an average coefficient close to 1. The new neural network hybrid architecture has short running time and low computational resource consumption, meeting the needs of practical applications. Full article

(This article belongs to the Special Issue Advanced Wide Bandgap Semiconductor Materials and Devices)

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18 pages, 4370 KiB

Open AccessArticle

The Multi-Objective Optimization of a Dual C-Type Gold Ribbon Interconnect Structure Considering Its Geometrical Parameter Fluctuation

by Guangmi Li, Song Xue, Jinyang Mu, Shaoyi Liu, Qiongfang Zhang, Wenzhi Wu, Zhihai Wang, Zhen Ma, Dongchao Diwu and Congsi Wang

Micromachines 2025, 16(8), 914; https://doi.org/10.3390/mi16080914 - 7 Aug 2025

Viewed by 185

Abstract

With the increasing demand for high integration, low cost, and large capacities in satellite systems, integrating the antenna and microwave component into the same system has become appealing to the satellite engineer. The dual C-type gold ribbon, performing as the key electromagnetic signal [...] Read more.

With the increasing demand for high integration, low cost, and large capacities in satellite systems, integrating the antenna and microwave component into the same system has become appealing to the satellite engineer. The dual C-type gold ribbon, performing as the key electromagnetic signal bridge between the microwave component and the antenna, has a significant impact on the electrical performance of satellite antennas. However, during its manufacturing and operating, the interconnection geometry undergoes deformation due to mounting errors and environmental loads. Consequently, these parasitic geometry parameters can significantly increase energy loss during the signal transmission. To address this issue, this paper has proposed a method for determining the design range of the geometrical parameters of the dual C-type gold ribbon, and applied it to the performance prediction of the microstrip antennas and the parameter optimization of the gold ribbon. In this study, a mechanical response analysis of the antennas in the operating environment has been carried out and the manufacturing disturbance has been considered to calculate the geometry fluctuation range. Then, the significance ranking of the geometry parameters has been determined and the key parameters have been selected. Finally, the chaos feedback adaptive whale optimization algorithm–back propagation neural network has been used as a surrogate model to establish the relationship between the geometry parameters and the antenna electromagnetic performance, and the multi-objective red-billed blue magpie optimization algorithm has been combined with the surrogate model to optimize the configuration parameters. This paper provides theoretical guidance for the interconnection geometry design and the optimization of the integration module of the antennas and microwave components. Full article

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21 pages, 15471 KiB

Open AccessArticle

Tribology of EDM Recast Layers Vis-À-Vis TIG Cladding Coatings: An Experimental Investigation

by Muhammad Adnan, Waqar Qureshi and Muhammad Umer

Micromachines 2025, 16(8), 913; https://doi.org/10.3390/mi16080913 - 7 Aug 2025

Viewed by 196

Abstract

Tribological performance is critical for the longevity and efficiency of machined components in industries such as aerospace, automotive, and biomedical. This study investigates whether electrical discharge machining recast layers can serve as a cost-effective and time-efficient alternative to conventional tungsten inert gas cladding [...] Read more.

Tribological performance is critical for the longevity and efficiency of machined components in industries such as aerospace, automotive, and biomedical. This study investigates whether electrical discharge machining recast layers can serve as a cost-effective and time-efficient alternative to conventional tungsten inert gas cladding coatings for enhancing surface properties. The samples were prepared using electrical discharge machining and tungsten inert gas cladding. For electrical discharge machining, various combinations of electrical and non-electrical parameters were applied using Taguchi’s L18 orthogonal array. Similarly, tungsten inert gas cladding coatings were prepared using a suitable combination of current, voltage, powder size, and speed. The samples were characterized using, scanning electron microscopy, optical microscopy, microhardness testing, tribological testing, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and profilometry. The electrical discharge machining recast layers exhibited superior tribological performance compared to tungsten inert gas cladding coatings. This improvement is attributed to the formation of carbides, such as TiC and Ti₆C_3.75. The coefficient of friction and specific wear rate were reduced by 11.11% and 1.57%, respectively, while microhardness increased by 10.93%. Abrasive wear was identified as the predominant wear mechanism. This study systematically compares electrical discharge machining recast layers with tungsten inert gas cladding coatings. The findings suggest that optimized electrical discharge machining recast layers can serve as effective coatings, offering cost and time savings. Full article

(This article belongs to the Special Issue Recent Developments in Electrical Discharge Machining Technology)

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18 pages, 19901 KiB

Open AccessArticle

A Novel Polysilicon-Fill-Strengthened Etch-Through 3D Trench Electrode Detector: Fabrication Methods and Electrical Property Simulations

by Xuran Zhu, Zheng Li, Zhiyu Liu, Tao Long, Jun Zhao, Xinqing Li, Manwen Liu and Meishan Wang

Micromachines 2025, 16(8), 912; https://doi.org/10.3390/mi16080912 - 6 Aug 2025

Viewed by 188

Abstract

Three-dimensional trench electrode silicon detectors play an important role in particle physics research, nuclear radiation detection, and other fields. A novel polysilicon-fill-strengthened etch-through 3D trench electrode detector is proposed to address the shortcomings of traditional 3D trench electrode silicon detectors; for example, the [...] Read more.

Three-dimensional trench electrode silicon detectors play an important role in particle physics research, nuclear radiation detection, and other fields. A novel polysilicon-fill-strengthened etch-through 3D trench electrode detector is proposed to address the shortcomings of traditional 3D trench electrode silicon detectors; for example, the distribution of non-uniform electric fields, asymmetric electric potential, and dead zone. The physical properties of the detector have been extensively and systematically studied. This study simulated the electric field, potential, electron concentration distribution, complete depletion voltage, leakage current, capacitance, transient current induced by incident particles, and weighting field distribution of the detector. It also systematically studied and analyzed the electrical characteristics of the detector. Compared to traditional 3D trench electrode silicon detectors, this new detector adopts a manufacturing process of double-side etching technology and double-side filling technology, which results in a more sensitive detector volume and higher electric field uniformity. In addition, the size of the detector unit is 120 µm × 120 µm × 340 µm; the structure has a small fully depleted voltage, reaching a fully depleted state at around 1.4 V, with a saturation leakage current of approximately

4.8 \times 10^{- 10} A

, and a geometric capacitance of about 99 fF. Full article

(This article belongs to the Special Issue Photonic and Optoelectronic Devices and Systems, Third Edition)

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11 pages, 2425 KiB

Open AccessArticle

Single-Layer High-Efficiency Metasurface for Multi-User Signal Enhancement

by Hui Jin, Peixuan Zhu, Rongrong Zhu, Bo Yang, Siqi Zhang and Huan Lu

Micromachines 2025, 16(8), 911; https://doi.org/10.3390/mi16080911 - 6 Aug 2025

Viewed by 239

Abstract

In multi-user wireless communication scenarios, signal degradation caused by channel fading and co-channel interference restricts system capacity, while traditional enhancement schemes face challenges of high coordination complexity and hardware integration. This paper proposes an electromagnetic focusing method using a single-layer transmissive passive metasurface. [...] Read more.

In multi-user wireless communication scenarios, signal degradation caused by channel fading and co-channel interference restricts system capacity, while traditional enhancement schemes face challenges of high coordination complexity and hardware integration. This paper proposes an electromagnetic focusing method using a single-layer transmissive passive metasurface. A high-efficiency metasurface array is fabricated based on PCB technology, which utilizes subwavelength units for wide-range phase modulation to construct a multi-user energy convergence model in the WiFi band. By optimizing phase gradients through the geometric phase principle, the metasurface achieves collaborative wavefront manipulation for multiple target regions with high transmission efficiency, reducing system complexity compared to traditional multi-layer structures. Measurements in a microwave anechoic chamber and tests in an office environment demonstrate that the metasurface can simultaneously create signal enhancement zones for multiple users, featuring stable focusing capability and environmental adaptability. This lightweight design facilitates deployment in dense networks, providing an effective solution for signal optimization in indoor distributed systems and IoT communications. Full article

(This article belongs to the Special Issue Novel Electromagnetic and Acoustic Devices)

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16 pages, 3174 KiB

Open AccessArticle

Efficient Particle Aggregation Through SSAW Phase Modulation

by Yiming Li, Zekai Li, Zuozhi Wei, Yiran Wang, Xudong Niu and Dongfang Liang

Micromachines 2025, 16(8), 910; https://doi.org/10.3390/mi16080910 - 5 Aug 2025

Viewed by 221

Abstract

In recent years, various devices utilizing surface acoustic waves (SAW) have emerged as powerful tools for manipulating particles and fluids in microchannels. Although they demonstrate a wide range of functionalities across diverse applications, existing devices still face limitations in flexibility, manipulation efficiency, and [...] Read more.

In recent years, various devices utilizing surface acoustic waves (SAW) have emerged as powerful tools for manipulating particles and fluids in microchannels. Although they demonstrate a wide range of functionalities across diverse applications, existing devices still face limitations in flexibility, manipulation efficiency, and spatial resolution. In this study, we developed a dual-sided standing surface acoustic wave (SSAW) device that simultaneously excites acoustic waves through two piezoelectric substrates positioned at the top and bottom of a microchannel. By fully exploiting the degrees of freedom offered by two pairs of interdigital transducers (IDTs) on each substrate, the system enables highly flexible control of microparticles. To explore its capability on particle aggregation, we developed a two-dimensional numerical model to investigate the influence of the SAW phase modulation on the established acoustic fields within the microchannel. Single-particle motion was first examined under the influence of the phase-modulated acoustic fields to form a reference for identifying effective phase modulation strategies. Key parameters, such as the phase changes and the duration of each phase modulation step, were determined to maximize the lateral motion while minimizing undesired vertical motion of the particle. Our dual-sided SSAW configuration, combined with novel dynamic phase modulation strategy, leads to rapid and precise aggregation of microparticles towards a single focal point. This study sheds new light on the design of acoustofluidic devices for efficient spatiotemporal particle concentration. Full article

(This article belongs to the Special Issue Surface and Bulk Acoustic Wave Devices, 2nd Edition)

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10 pages, 3553 KiB

Open AccessArticle

A Trench Heterojunction Diode-Integrated 4H-SiC LDMOS with Enhanced Reverse Recovery Characteristics

by Yanjuan Liu, Fangfei Bai and Junpeng Fang

Micromachines 2025, 16(8), 909; https://doi.org/10.3390/mi16080909 - 4 Aug 2025

Viewed by 228

Abstract

In this paper, a novel 4H-SiC LDMOS structure with a trench heterojunction in the source (referred as to THD-LDMOS) is proposed and investigated for the first time, to enhance the reverse recovery performance of its parasitic diode. Compared with 4H-SiC, silicon has a [...] Read more.

In this paper, a novel 4H-SiC LDMOS structure with a trench heterojunction in the source (referred as to THD-LDMOS) is proposed and investigated for the first time, to enhance the reverse recovery performance of its parasitic diode. Compared with 4H-SiC, silicon has a smaller band energy, which results in a lower built-in potential for the junction formed by P+ polysilicon and a 4N-SiC N-drift region. A trench P+ polysilicon is introduced in the source side, forming a heterojunction with the N-drift region, and this heterojunction is unipolar and connected in parallel with the body PiN diode. When the LDMOS operates as a freewheeling diode, the trench heterojunction conducts first, preventing the parasitic PiN from turning on and thereby significantly reducing the number of carriers in the N-drift region. Consequently, THD-LDMOS exhibits superior reverse recovery characteristics. The simulation results indicate that the reverse recovery peak current and reverse recovery charge of THD-LDMOS are reduced by 55.5% and 77.6%, respectively, while the other basic electrical characteristics remains unaffected. Full article

(This article belongs to the Special Issue Advanced Wide Bandgap Semiconductor Materials and Devices)

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14 pages, 3520 KiB

Open AccessArticle

Design and Fabrication of Embedded Microchannel Cooling Solutions for High-Power-Density Semiconductor Devices

by Yu Fu, Guangbao Shan, Xiaofei Zhang, Lizheng Zhao and Yintang Yang

Micromachines 2025, 16(8), 908; https://doi.org/10.3390/mi16080908 - 4 Aug 2025

Viewed by 467

Abstract

The rapid development of high-power-density semiconductor devices has rendered conventional thermal management techniques inadequate for handling their extreme heat fluxes. This manuscript presents and implements an embedded microchannel cooling solution for such devices. By directly integrating micropillar arrays within the near-junction region of [...] Read more.

The rapid development of high-power-density semiconductor devices has rendered conventional thermal management techniques inadequate for handling their extreme heat fluxes. This manuscript presents and implements an embedded microchannel cooling solution for such devices. By directly integrating micropillar arrays within the near-junction region of the substrate, efficient forced convection and flow boiling mechanisms are achieved. Finite element analysis was first employed to conduct thermo–fluid–structure simulations of micropillar arrays with different geometries. Subsequently, based on our simulation results, a complete multilayer microstructure fabrication process was developed and integrated, including critical steps such as deep reactive ion etching (DRIE), surface hydrophilic/hydrophobic functionalization, and gold–stannum (Au-Sn) eutectic bonding. Finally, an experimental test platform was established to systematically evaluate the thermal performance of the fabricated devices under heat fluxes of up to 1200 W/cm². Our experimental results demonstrate that this solution effectively maintains the device operating temperature at 46.7 °C, achieving a mere 27.9 K temperature rise and exhibiting exceptional thermal management capabilities. This manuscript provides a feasible, efficient technical pathway for addressing extreme heat dissipation challenges in next-generation electronic devices, while offering notable references in structural design, micro/nanofabrication, and experimental validation for related fields. Full article

(This article belongs to the Special Issue Flexible and Biodegradable Electronics and Novel Semiconductor Devices)

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15 pages, 6688 KiB

Open AccessArticle

Integrated Additive Manufacturing of TGV Interconnects and High-Frequency Circuits via Bipolar-Controlled EHD Jetting

by Dongqiao Bai, Jin Huang, Hongxiao Gong, Jianjun Wang, Yunna Pu, Jiaying Zhang, Peng Sun, Zihan Zhu, Pan Li, Huagui Wang, Pengbing Zhao and Chaoyu Liang

Micromachines 2025, 16(8), 907; https://doi.org/10.3390/mi16080907 - 2 Aug 2025

Viewed by 280

Abstract

Electrohydrodynamic (EHD) printing offers mask-free, high-resolution deposition across a broad range of ink viscosities, yet combining void-free filling of high-aspect-ratio through-glass vias (TGVs) with ultrafine drop-on-demand (DOD) line printing on the same platform requires balancing conflicting requirements: for example, high field strengths to [...] Read more.

Electrohydrodynamic (EHD) printing offers mask-free, high-resolution deposition across a broad range of ink viscosities, yet combining void-free filling of high-aspect-ratio through-glass vias (TGVs) with ultrafine drop-on-demand (DOD) line printing on the same platform requires balancing conflicting requirements: for example, high field strengths to drive ink into deep and narrow vias; sufficiently high ink viscosity to prevent gravity-induced leakage; and stable meniscus dynamics to avoid satellite droplets and charge accumulation on the glass surface. By coupling electrostatic field analysis with transient level-set simulations, we establish a dimensionless regime map that delineates stable cone-jetting regime; these predictions are validated by high-speed imaging and surface profilometry. Operating within this window, the platform achieves complete, void-free filling of 200 µm × 1.52 mm TGVs and continuous 10 µm-wide traces in a single print pass. Demonstrating its capabilities, we fabricate transparent Ku-band substrate-integrated waveguide antennas on borosilicate glass: the printed vias and arc feed elements exhibit a reflection coefficient minimum of −18 dB at 14.2 GHz, a −10 dB bandwidth of 12.8–16.2 GHz, and an 8 dBi peak gain with 37° beam tilt, closely matching full-wave predictions. This physics-driven, all-in-one EHD approach provides a scalable route to high-performance, glass-integrated RF devices and transparent electronics. Full article

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23 pages, 3916 KiB

Open AccessArticle

Leveraging Wearable Sensors for the Identification and Prediction of Defensive Pessimism Personality Traits

by You Zhou, Dongfen Li, Bowen Deng and Weiqian Liang

Micromachines 2025, 16(8), 906; https://doi.org/10.3390/mi16080906 - 2 Aug 2025

Viewed by 332

Abstract

Defensive pessimism, an important emotion regulation and motivation strategy, has increasingly attracted scholarly attention in psychology. Recently, sensor-based methods have begun to supplement or replace traditional questionnaire surveys in personality research. However, current approaches for collecting vital signs data face several challenges, including [...] Read more.

Defensive pessimism, an important emotion regulation and motivation strategy, has increasingly attracted scholarly attention in psychology. Recently, sensor-based methods have begun to supplement or replace traditional questionnaire surveys in personality research. However, current approaches for collecting vital signs data face several challenges, including limited monitoring durations, significant data deviations, and susceptibility to external interference. This paper proposes a novel approach using a NiCr/NiSi alloy film temperature sensor, which has a K-type structure and flexible piezoelectric pressure sensor to identify and predict defensive pessimism personality traits. Experimental results indicate that the Seebeck coefficients for K-, T-, and E-type thermocouples are approximately 41 μV/°C, 39 μV/°C, and 57 μV/°C, respectively, which align closely with national standards and exhibit good consistency across multiple experimental groups. Moreover, radial artery frequency experiments demonstrate a strong linear relationship between pulse rate and the intensity of external stimuli, where stronger stimuli correspond to faster pulse rates. Simulation experiments further reveal a high correlation between radial artery pulse frequency and skin temperature, and a regression model based on the physiological sensor data shows a good fit (p < 0.05). These findings verify the feasibility of using temperature and flexible piezoelectric pressure sensors to identify and predict defensive pessimism personality characteristics. Full article

(This article belongs to the Special Issue Structural Analyses and Designs for Flexible/Stretchable Electronics, 3rd Edition)

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14 pages, 2426 KiB

Open AccessArticle

A Novel Integrated Inertial Navigation System with a Single-Axis Cold Atom Interferometer Gyroscope Based on Numerical Studies

by Zihao Chen, Fangjun Qin, Sibin Lu, Runbing Li, Min Jiang, Yihao Wang, Jiahao Fu and Chuan Sun

Micromachines 2025, 16(8), 905; https://doi.org/10.3390/mi16080905 - 2 Aug 2025

Viewed by 262

Abstract

Inertial navigation systems (INSs) exhibit distinctive characteristics, such as long-duration operation, full autonomy, and exceptional covertness compared to other navigation systems. However, errors are accumulated over time due to operational principles and the limitations of sensors. To address this problem, this study theoretically [...] Read more.

Inertial navigation systems (INSs) exhibit distinctive characteristics, such as long-duration operation, full autonomy, and exceptional covertness compared to other navigation systems. However, errors are accumulated over time due to operational principles and the limitations of sensors. To address this problem, this study theoretically explores a numerically simulated integrated inertial navigation system consisting of a single-axis cold atom interferometer gyroscope (CAIG) and a conventional inertial measurement unit (IMU). The system leverages the low bias and drift of the CAIG and the high sampling rate of the conventional IMU to obtain more accurate navigation information. Furthermore, an adaptive gradient ascent (AGA) method is proposed to estimate the variance of the measurement noise online for the Kalman filter. It was found that errors of latitude, longitude, and positioning are reduced by 43.9%, 32.6%, and 32.3% compared with the conventional IMU over 24 h. On this basis, errors from inertial sensor drift could be further reduced by the online Kalman filter. Full article

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13 pages, 1944 KiB

Open AccessArticle

A Sliding Microfluidic Chip-Integrated Colorimetric Biosensor Using MnO₂ Nanoflowers for Rapid Salmonella Detection

by Yidan Niu, Juntao Jiang, Xin Zhi, Jiahui An and Yuhe Wang

Micromachines 2025, 16(8), 904; https://doi.org/10.3390/mi16080904 - 31 Jul 2025

Viewed by 247

Abstract

Rapid screening of foodborne pathogens is critical for food safety, yet current detection techniques often suffer from low efficiency and complexity. In this study, we developed a sliding microfluidic colorimetric biosensor for the fast, sensitive, and multiplex detection of Salmonella. First, the [...] Read more.

Rapid screening of foodborne pathogens is critical for food safety, yet current detection techniques often suffer from low efficiency and complexity. In this study, we developed a sliding microfluidic colorimetric biosensor for the fast, sensitive, and multiplex detection of Salmonella. First, the target bacteria were specifically captured by antibody-functionalized magnetic nanoparticles in the microfluidic chip, forming magnetic bead–bacteria complexes. Then, through motor-assisted sliding of the chip, manganese dioxide (MnO₂) nanoflowers conjugated with secondary antibodies were introduced to bind the captured bacteria, generating a dual-antibody sandwich structure. Finally, a second sliding step brought the complexes into contact with a chromogenic substrate, where the MnO₂ nanoflowers catalyzed a colorimetric reaction, and the resulting signal was used to quantify the Salmonella concentration. Under optimized conditions, the biosensor achieved a detection limit of 10 CFU/mL within 20 min. In spiked pork samples, the average recovery rate of Salmonella ranged from 94.9% to 125.4%, with a coefficient of variation between 4.0% and 6.8%. By integrating mixing, separation, washing, catalysis, and detection into a single chip, this microfluidic biosensor offers a user-friendly, time-efficient, and highly sensitive platform, showing great potential for the on-site detection of foodborne pathogens. Full article

(This article belongs to the Section B1: Biosensors)

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38 pages, 5463 KiB

Open AccessArticle

Configuration Synthesis and Performance Analysis of 1T2R Decoupled Wheel-Legged Reconfigurable Mechanism

by Jingjing Shi, Ruiqin Li and Wenxiao Guo

Micromachines 2025, 16(8), 903; https://doi.org/10.3390/mi16080903 - 31 Jul 2025

Viewed by 267

Abstract

A method for configuration synthesis of a reconfigurable decoupled parallel mechanical leg is proposed. In addition, a configuration evaluation index is proposed to evaluate the synthesized configurations and select the optimal one. Kinematic analysis and performance optimization of the selected mechanism’s configuration are [...] Read more.

A method for configuration synthesis of a reconfigurable decoupled parallel mechanical leg is proposed. In addition, a configuration evaluation index is proposed to evaluate the synthesized configurations and select the optimal one. Kinematic analysis and performance optimization of the selected mechanism’s configuration are carried out, and the motion mode of the robot’s reconfigurable mechanical leg is selected according to the task requirements. Then, the robot’s gait in walking mode is planned. Firstly, based on bionic principles, the motion characteristics of a mechanical leg based on a mammalian model and an insect model were analyzed. The input and output characteristics of the mechanism were analyzed to obtain the reconfiguration principle of the mechanism. Using type synthesis theory for the decoupled parallel mechanism, the configuration synthesis of the chain was carried out, and the constraint mode of the mechanical leg was determined according to the constraint property of the chain and the motion characteristics of the moving platform. Secondly, an evaluation index for the complexity of the reconfigurable mechanical leg structure was developed, and the synthesized mechanism was further analyzed and evaluated to select the mechanical leg’s configuration. Thirdly, the inverse position equations were established for the mechanical leg in the two motion modes, and its Jacobian matrix was derived. The degrees of freedom of the mechanism are completely decoupled in the two motion modes. Then, the workspace and motion/force transmission performance of the mechanical leg in the two motion modes were analyzed. Based on the weighted standard deviation of the motion/force transmission performance, the global performance fluctuation index of the mechanical leg motion/force transmission is defined, and the structural size parameters of the mechanical leg are optimized with the performance index as the optimization objective function. Finally, with the reconfigurable mechanical leg in the insect mode, the robot’s gait in the walking operation mode is planned according to the static stability criterion. Full article

(This article belongs to the Special Issue Soft Actuators: Design, Fabrication and Applications, 2nd Edition)

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42 pages, 4490 KiB

Open AccessReview

Continuous Monitoring with AI-Enhanced BioMEMS Sensors: A Focus on Sustainable Energy Harvesting and Predictive Analytics

by Mingchen Cai, Hao Sun, Tianyue Yang, Hongxin Hu, Xubing Li and Yuan Jia

Micromachines 2025, 16(8), 902; https://doi.org/10.3390/mi16080902 - 31 Jul 2025

Viewed by 481

Abstract

Continuous monitoring of environmental and physiological parameters is essential for early diagnostics, real-time decision making, and intelligent system adaptation. Recent advancements in bio-microelectromechanical systems (BioMEMS) sensors have significantly enhanced our ability to track key metrics in real time. However, continuous monitoring demands sustainable [...] Read more.

Continuous monitoring of environmental and physiological parameters is essential for early diagnostics, real-time decision making, and intelligent system adaptation. Recent advancements in bio-microelectromechanical systems (BioMEMS) sensors have significantly enhanced our ability to track key metrics in real time. However, continuous monitoring demands sustainable energy supply solutions, especially for on-site energy replenishment in areas with limited resources. Artificial intelligence (AI), particularly large language models, offers new avenues for interpreting the vast amounts of data generated by these sensors. Despite this potential, fully integrated systems that combine self-powered BioMEMS sensing with AI-based analytics remain in the early stages of development. This review first examines the evolution of BioMEMS sensors, focusing on advances in sensing materials, micro/nano-scale architectures, and fabrication techniques that enable high sensitivity, flexibility, and biocompatibility for continuous monitoring applications. We then examine recent advances in energy harvesting technologies, such as piezoelectric nanogenerators, triboelectric nanogenerators and moisture electricity generators, which enable self-powered BioMEMS sensors to operate continuously and reducereliance on traditional batteries. Finally, we discuss the role of AI in BioMEMS sensing, particularly in predictive analytics, to analyze continuous monitoring data, identify patterns, trends, and anomalies, and transform this data into actionable insights. This comprehensive analysis aims to provide a roadmap for future continuous BioMEMS sensing, revealing the potential unlocked by combining materials science, energy harvesting, and artificial intelligence. Full article

(This article belongs to the Special Issue Advancing MEMS/MOEMS Sensors: AI-Driven Optimization and Emerging Applications)

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11 pages, 3403 KiB

Open AccessArticle

Optical Design and Lens Fabrication for Automotive Thermal Imaging Using Chalcogenide Glass

by Young-Soo Choi and Ji-Kwan Kim

Micromachines 2025, 16(8), 901; https://doi.org/10.3390/mi16080901 - 31 Jul 2025

Viewed by 231

Abstract

This paper is about the design and fabrication of infrared lenses, which are the core components of thermal imaging cameras to be mounted on vehicles. To produce an athermalized optical system, chalcogenide glass (As₄₀Se₆₀) with a lower thermo-optic coefficient [...] Read more.

This paper is about the design and fabrication of infrared lenses, which are the core components of thermal imaging cameras to be mounted on vehicles. To produce an athermalized optical system, chalcogenide glass (As₄₀Se₆₀) with a lower thermo-optic coefficient (dn/dT) than germanium was adopted as a lens material, and each lens was designed so that defocus occurs in opposite directions depending on temperature. The designed lens was fabricated using a compression molding method, and the molded lenses showed less than 1.5 μm of form error (PV) using a mold iteration process. Through evaluations of MTF and thermal images obtained from the lens module, it was judged that this optical design process is obtainable. Full article

(This article belongs to the Collection Optical MEMS: Design, Fabrication, Control, Modeling and Developments)

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24 pages, 1835 KiB

Open AccessReview

Multidomain Molecular Sensor Devices, Systems, and Algorithms for Improved Physiological Monitoring

by Lianna D. Soriano, Shao-Xiang Go, Lunna Li, Natasa Bajalovic and Desmond K. Loke

Micromachines 2025, 16(8), 900; https://doi.org/10.3390/mi16080900 - 31 Jul 2025

Viewed by 212

Abstract

Molecular sensor systems, e.g., implantables and wearables, provide extensive health-related monitoring. Glucose sensor systems have historically prevailed in wearable bioanalysis applications due to their continuous and reliable glucose monitoring, a feat not yet accomplished for other biomarkers. However, the advancement of reagentless detection [...] Read more.

Molecular sensor systems, e.g., implantables and wearables, provide extensive health-related monitoring. Glucose sensor systems have historically prevailed in wearable bioanalysis applications due to their continuous and reliable glucose monitoring, a feat not yet accomplished for other biomarkers. However, the advancement of reagentless detection methodologies may facilitate the creation of molecular sensor systems for multiple analytes. Improving the sensitivity and selectivity of molecular sensor systems is also crucial for biomarker detection under intricate physiological circumstances. The term multidomain molecular sensor systems is utilized to refer, in general, to both biological and chemical sensor systems. This review examines methodologies for enhancing signal amplification, improving selectivity, and facilitating reagentless detection in multidomain molecular sensor devices. The review also analyzes the fundamental components of multidomain molecular sensor systems, including substrate materials, bodily fluids, power, and decision-making units. The review article further investigates how extensive data gathered from multidomain molecular sensor systems, in conjunction with current data processing algorithms, facilitate biomarker detection for precision medicine. Full article

(This article belongs to the Special Issue Nanoparticle-Based (Bio)Sensors for Biomedical and Environmental Monitoring)

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15 pages, 3565 KiB

Open AccessArticle

Controlled PolyDMAEMA Functionalization of Titanium Surfaces via Graft-To and Graft-From Strategies

by Chiara Frezza, Susanna Romano, Daniele Rocco, Giancarlo Masci, Giovanni Sotgiu, Monica Orsini and Serena De Santis

Micromachines 2025, 16(8), 899; https://doi.org/10.3390/mi16080899 - 31 Jul 2025

Viewed by 215

Abstract

Titanium is widely recognized as an interesting material for electrodes due to its excellent corrosion resistance, mechanical strength, and biocompatibility. However, further functionalization is often necessary to impart advanced interfacial properties, such as selective ion transport or stimuli responsiveness. In this context, the [...] Read more.

Titanium is widely recognized as an interesting material for electrodes due to its excellent corrosion resistance, mechanical strength, and biocompatibility. However, further functionalization is often necessary to impart advanced interfacial properties, such as selective ion transport or stimuli responsiveness. In this context, the integration of smart polymers, such as poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)—noted for its dual pH- and thermo-responsive behavior—has emerged as a promising approach to tailor surface properties for next-generation devices. This work compares two covalent immobilization strategies for PDMAEMA on titanium: the “graft-to” method, involving the attachment of pre-synthesized polymer chains, and the “graft-from” method, based on surface-initiated polymerization. The resulting materials were characterized with size exclusion chromatography (SEC) for molecular weight, Fourier-transform infrared spectroscopy (FTIR) for chemical structure, scanning electron microscopy (SEM) for surface morphology, and contact angle measurements for wettability. Electrochemical impedance spectroscopy and polarization studies were used to assess electrochemical performance. Both strategies yielded uniform and stable coatings, with the mode of grafting influencing both surface morphology and functional stability. These findings provide valuable insights into the development of adaptive, stimuli-responsive titanium-based interfaces in advanced electrochemical systems. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications, 2nd Edition)

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15 pages, 5631 KiB

Open AccessArticle

Design and Evaluation of a Capacitive Micromachined Ultrasonic Transducer(CMUT) Linear Array System for Thickness Measurement of Marine Structures Under Varying Environmental Conditions

by Changde He, Mengke Luo, Hanchi Chai, Hongliang Wang, Guojun Zhang, Renxin Wang, Jiangong Cui, Yuhua Yang, Wendong Zhang and Licheng Jia

Micromachines 2025, 16(8), 898; https://doi.org/10.3390/mi16080898 - 31 Jul 2025

Viewed by 244

Abstract

This paper presents the design, fabrication, and experimental evaluation of a capacitive micromachined ultrasonic transducer (CMUT) linear array for non-contact thickness measurement of marine engineering structures. A 16-element CMUT array was fabricated using a silicon–silicon wafer bonding process, and encapsulated in polyurethane to [...] Read more.

This paper presents the design, fabrication, and experimental evaluation of a capacitive micromachined ultrasonic transducer (CMUT) linear array for non-contact thickness measurement of marine engineering structures. A 16-element CMUT array was fabricated using a silicon–silicon wafer bonding process, and encapsulated in polyurethane to ensure acoustic impedance matching and environmental protection in underwater conditions. The acoustic performance of the encapsulated CMUT was characterized using standard piezoelectric transducers as reference. The array achieved a transmitting sensitivity of 146.82 dB and a receiving sensitivity of −229.55 dB at 1 MHz. A complete thickness detection system was developed by integrating the CMUT array with a custom transceiver circuit and implementing a time-of-flight (ToF) measurement algorithm. To evaluate environmental robustness, systematic experiments were conducted under varying water temperatures and salinity levels. The results demonstrate that the absolute thickness measurement error remains within ±0.1 mm under all tested conditions, satisfying the accuracy requirements for marine structural health monitoring. The results validate the feasibility of CMUT-based systems for precise and stable thickness measurement in underwater environments, and support their application in non-destructive evaluation of marine infrastructure. Full article

(This article belongs to the Special Issue MEMS/NEMS Devices and Applications, 3rd Edition)

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Micromachines, Volume 16, Issue 8 (August 2025) – 91 articles

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