Micromachines

23 pages, 3253 KB

Open AccessFeature PaperEditor’s ChoiceReview

Overcoming Challenges in Silicon Anodes: The Role of Electrolyte Additives and Solid-State Electrolytes

by Jinsik Nam, Hanbyeol Lee and Oh B. Chae

Micromachines 2025, 16(7), 800; https://doi.org/10.3390/mi16070800 - 9 Jul 2025

Viewed by 1422

Silicon-based anodes have emerged as promising candidates for advanced lithium-ion batteries (LIBs) owing to their outstanding lithium storage capacity; however, the commercial implementation of silicon-based anodes is hindered primarily by their significant volumetric changes and the resulting solid electrolyte interphase (SEI) instability during [...] Read more.

Silicon-based anodes have emerged as promising candidates for advanced lithium-ion batteries (LIBs) owing to their outstanding lithium storage capacity; however, the commercial implementation of silicon-based anodes is hindered primarily by their significant volumetric changes and the resulting solid electrolyte interphase (SEI) instability during the lithiation/delithiation process. To overcome these issues, electrolyte optimization, particularly through the use of functional additives and solid-state electrolytes, has attracted significant research attention. In this paper, we review the recent developments in electrolyte additives, such as vinylene carbonate, fluoroethylene carbonate, and silane-based additives, and new additives, such as dimethylacetamide, that improve the SEI stability and overall electrochemical performance of silicon-based anodes. We also discuss the role of solid electrolytes, including oxides, sulfides, and polymer-based systems, in mitigating the volume changes in Si and improving safety. Such approaches can effectively enhance both the longevity and capacity retention of silicon-based anodes. Despite significant progress, further studies are essential to optimize electrolyte formulation and solve interfacial problems. Integrating these advances with improved electrode designs and anode materials is critical for realizing the full potential of silicon-based anodes in high-performance LIBs, particularly in electric vehicles and portable electronics. Full article

(This article belongs to the Special Issue Nanomaterials for Micro/Nano Devices, 2nd Edition)

► Show Figures

Figure 1

39 pages, 7348 KB

Open AccessFeature PaperEditor’s ChoiceReview

Artificial Intelligence Control Methodologies for Shape Memory Alloy Actuators: A Systematic Review and Performance Analysis

by Stefano Rodinò, Giuseppe Rota, Matteo Chiodo, Antonio Corigliano and Carmine Maletta

Micromachines 2025, 16(7), 780; https://doi.org/10.3390/mi16070780 - 30 Jun 2025

Viewed by 671

Abstract

Shape Memory Alloy (SMA) actuators are pivotal in modern engineering due to their unique thermomechanical properties, but their inherent non-linearities, hysteresis, and temperature sensitivity pose significant control challenges. This systematic review evaluates artificial intelligence (AI)-based control methodologies to address these limitations, analyzing their [...] Read more.

Shape Memory Alloy (SMA) actuators are pivotal in modern engineering due to their unique thermomechanical properties, but their inherent non-linearities, hysteresis, and temperature sensitivity pose significant control challenges. This systematic review evaluates artificial intelligence (AI)-based control methodologies to address these limitations, analyzing their efficacy in enhancing precision, adaptability, and reliability for SMA and Magnetic SMA (MSMA) systems. A PRISMA-guided literature review (2003–2025) identified 24 studies, which were categorized by control architectures (hybrid AI-linear, pure AI, adaptive, and model predictive control) and evaluated through quantitative metrics, including Root Mean Square Error (RMSE%) and a weighted scoring system for experimental rigor. Results revealed hybrid AI-linear controllers as the dominant approach (36%), with online-trained neural networks achieving superior accuracy (+2.4%) over offline methods. Feedforward neural networks outperformed recurrent architectures (+3.1%), while Model Predictive Control (MPC) excelled for SMA actuators (+5.8% accuracy) but underperformed for MSMAs (−7.7%). Sensorless strategies proved advantageous for MSMAs (+5.0%), leveraging intrinsic material properties like electrical resistance for state estimation. The analysis underscores AI’s capacity to mitigate hysteresis and non-linear dynamics, though material-specific optimization is critical: SMA systems favor dynamic control and MPC, whereas MSMAs benefit from sensorless AI and pure neural networks. Challenges persist in computational demands for online training and reinforcement learning’s exploration–exploitation trade-offs. Future research should prioritize adaptive algorithms for fatigue compensation, lightweight AI models for embedded deployment, and standardized benchmarking to bridge material-specific performance gaps. This synthesis establishes AI as a transformative paradigm for SMA actuation, enabling precise control in aerospace, biomedical, and soft robotics applications. Full article

(This article belongs to the Special Issue Design and Real Time Implementation of Intelligent Control Schemes for Actuators)

► Show Figures

Figure 1

20 pages, 23523 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Wrist Brace with Integrated Piezoelectric Sensors for Real-Time Biomechanical Monitoring in Weightlifting

by Sofia Garcia, Ethan Ortega, Mohammad Alghamaz, Alwathiqbellah Ibrahim and En-Tze Chong

Micromachines 2025, 16(7), 775; https://doi.org/10.3390/mi16070775 - 30 Jun 2025

Viewed by 468

Abstract

This study presents a self-powered smart wrist brace integrated with a piezoelectric sensor for real-time biomechanical monitoring during weightlifting activities. The system was designed to quantify wrist flexion across multiple loading conditions (0 kg, 0.5 kg, and 1.0 kg), leveraging mechanical strain-induced voltage [...] Read more.

This study presents a self-powered smart wrist brace integrated with a piezoelectric sensor for real-time biomechanical monitoring during weightlifting activities. The system was designed to quantify wrist flexion across multiple loading conditions (0 kg, 0.5 kg, and 1.0 kg), leveraging mechanical strain-induced voltage generation to capture angular displacement. A flexible PVDF film was embedded within a custom-fitted wrist brace and tested on male and female participants performing controlled wrist flexion. The resulting voltage signals were analyzed to extract root-mean-square (RMS) outputs, calibration curves, and sensitivity metrics. To interpret the experimental results analytically, a lumped-parameter cantilever beam model was developed, linking wrist flexion angles to piezoelectric voltage output based on mechanical deformation theory. The model assumed a linear relationship between wrist angle and induced strain, enabling theoretical voltage prediction through simplified material and geometric parameters. Model-predicted voltage responses were compared with experimental measurements, demonstrating a good agreement and validating the mechanical-electrical coupling approach. Experimental results revealed consistent voltage increases with both wrist angle and applied load, and regression analysis demonstrated strong linear or mildly nonlinear fits with high

R^{2}

values (up to 0.994) across all conditions. Furthermore, surface plots and strain sensitivity analyses highlighted the system’s responsiveness to simultaneous angular and loading changes. These findings validate the smart wrist brace as a reliable, low-power biomechanical monitoring tool, with promising applications in injury prevention, rehabilitation, and real-time athletic performance feedback. Full article

(This article belongs to the Special Issue Next-Generation Wearable Technologies: Integrating Smart Sensing, Biomedical Innovation, and Sustainable Energy Solutions)

► Show Figures

Figure 1

23 pages, 4929 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Low Phase Noise, Dual-Frequency Pierce MEMS Oscillators with Direct Print Additively Manufactured Amplifier Circuits

by Liguan Li, Di Lan, Xu Han, Tinghung Liu, Julio Dewdney, Adnan Zaman, Ugur Guneroglu, Carlos Molina Martinez and Jing Wang

Micromachines 2025, 16(7), 755; https://doi.org/10.3390/mi16070755 - 26 Jun 2025

Cited by 1 | Viewed by 584

Abstract

This paper presents the first demonstration and comparison of two identical oscillator circuits employing piezoelectric zinc oxide (ZnO) microelectromechanical systems (MEMS) resonators, implemented on conventional printed-circuit-board (PCB) and three-dimensional (3D)-printed acrylonitrile butadiene styrene (ABS) substrates. Both oscillators operate simultaneously at dual frequencies (260 [...] Read more.

This paper presents the first demonstration and comparison of two identical oscillator circuits employing piezoelectric zinc oxide (ZnO) microelectromechanical systems (MEMS) resonators, implemented on conventional printed-circuit-board (PCB) and three-dimensional (3D)-printed acrylonitrile butadiene styrene (ABS) substrates. Both oscillators operate simultaneously at dual frequencies (260 MHz and 437 MHz) without the need for additional circuitry. The MEMS resonators, fabricated on silicon-on-insulator (SOI) wafers, exhibit high-quality factors (Q), ensuring superior phase noise performance. Experimental results indicate that the oscillator packaged using 3D-printed chip-carrier assembly achieves a 2–3 dB improvement in phase noise compared to the PCB-based oscillator, attributed to the ABS substrate’s lower dielectric loss and reduced parasitic effects at radio frequency (RF). Specifically, phase noise values between −84 and −77 dBc/Hz at 1 kHz offset and a noise floor of −163 dBc/Hz at far-from-carrier offset were achieved. Additionally, the 3D-printed ABS-based oscillator delivers notably higher output power (4.575 dBm at 260 MHz and 0.147 dBm at 437 MHz). To facilitate modular characterization, advanced packaging techniques leveraging precise 3D-printed encapsulation with sub-100 μm lateral interconnects were employed. These ensured robust packaging integrity without compromising oscillator performance. Furthermore, a comparison between two transistor technologies—a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) and an enhancement-mode pseudomorphic high-electron-mobility transistor (E-pHEMT)—demonstrated that SiGe HBT transistors provide superior phase noise characteristics at close-to-carrier offset frequencies, with a significant 11 dB improvement observed at 1 kHz offset. These results highlight the promising potential of 3D-printed chip-carrier packaging techniques in high-performance MEMS oscillator applications. Full article

(This article belongs to the Section E：Engineering and Technology)

► Show Figures

Figure 1

24 pages, 11574 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Using Adaptive Surrogate Models to Accelerate Multi-Objective Design Optimization of MEMS

by Ali Nazari, Armin Aghajani, Phiona Buhr, Byoungyoul Park, Yunli Wang and Cyrus Shafai

Micromachines 2025, 16(7), 753; https://doi.org/10.3390/mi16070753 - 26 Jun 2025

Viewed by 3172

Abstract

This study presents a comprehensive multi-objective optimization framework specifically designed for micro-electromechanical systems (MEMS). The framework integrates both traditional and adaptive optimization techniques, named Surrogate-Assisted Multi-Objective Optimization (SAMOO) and Adaptive-SAMOO (A-SAMOO), respectively. By addressing key limitations of traditional approaches, such as the consideration [...] Read more.

This study presents a comprehensive multi-objective optimization framework specifically designed for micro-electromechanical systems (MEMS). The framework integrates both traditional and adaptive optimization techniques, named Surrogate-Assisted Multi-Objective Optimization (SAMOO) and Adaptive-SAMOO (A-SAMOO), respectively. By addressing key limitations of traditional approaches, such as the consideration of objective constraints and the provision of multiple design options, the proposed framework enhances both flexibility and practical applicability. Results show that adaptive optimization outperforms traditional offline methods by delivering a greater number and higher quality of optimal solutions while requiring fewer finite element method simulations. The adaptive approach showed a significant advantage by attaining high-quality solutions while requiring only 2.8% of the finite element method (FEM) evaluations compared to traditional methods that do not incorporate surrogate models. This performance boost highlights the advantages of online learning in enhancing the accuracy, speed, and diversity of solutions in MEMS optimization. These optimization schemes were tested on multiple MEMS devices with varying physics and complexities, specifically the U-shaped Lorentz force actuator, serpentine Lorentz force actuator, and thermal actuator. The results highlight the robustness and versatility of the proposed methods, particularly in addressing cases involving discrete design variables and strict objective constraints. This comprehensive, step-by-step framework serves as a valuable resource for researchers and practitioners aiming to optimize MEMS designs from the ground up, providing a reliable and effective approach to multi-objective optimization in MEMS applications. Full article

(This article belongs to the Special Issue MEMS Actuators and Their Applications)

► Show Figures

Figure 1

13 pages, 4027 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Dialysis Membrane-Integrated Microfluidic Device for Controlled Drug Retention and Nutrient Supply

by Hajime Miyashita, Yuya Ito, Kenta Shinha, Hiroko Nakamura and Hiroshi Kimura

Micromachines 2025, 16(7), 745; https://doi.org/10.3390/mi16070745 - 25 Jun 2025

Viewed by 531

Abstract

Traditional pre-clinical drug evaluation methods, including animal experiments and static cell cultures using human-derived cells, face critical limitations such as interspecies differences, ethical concerns, and poor physiological relevance. More recently, microphysiological systems (MPSs) that use microfluidic devices to mimic in vivo conditions have [...] Read more.

Traditional pre-clinical drug evaluation methods, including animal experiments and static cell cultures using human-derived cells, face critical limitations such as interspecies differences, ethical concerns, and poor physiological relevance. More recently, microphysiological systems (MPSs) that use microfluidic devices to mimic in vivo conditions have emerged as promising platforms. By enabling perfusion cell culture and incorporating human-derived cells, MPSs can evaluate drug efficacy and toxicity in a more human-relevant manner. However, standard MPS protocols rely on discrete medium changes, causing abrupt changes in drug concentrations that do not reflect the continuous pharmacokinetics seen in vivo. To overcome this limitation, we developed a Dialysis Membrane-integrated Microfluidic Device (DMiMD) which maintains continuous drug concentrations through selective medium change via a dialysis membrane. The membrane’s molecular weight cut-off (MWCO) enables the retention of high-molecular-weight drugs while facilitating the passage of essential low-molecular-weight nutrients such as glucose. We validated the membrane’s molecular selectivity and confirmed effective nutrient supply using cells. Additionally, anticancer drug efficacy was evaluated under continuously changing drug concentrations, demonstrating that the DMiMD successfully mimics in vivo drug exposure dynamics. These results indicate that the DMiMD offers a robust in vitro platform for accurate assessment of drug efficacy and toxicity, bridging the gap between conventional static assays and the physiological complexities of the human body. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

► Show Figures

Figure 1

14 pages, 2324 KB

Open AccessFeature PaperEditor’s ChoiceArticle

An Organ-on-a-Chip Modular Platform with Integrated Immunobiosensors for Monitoring the Extracellular Environment

by Anastasia Kanioura, Myrto Kyriaki Filippidou, Dimitra Tsounidi, Panagiota S. Petrou, Stavros Chatzandroulis and Angeliki Tserepi

Micromachines 2025, 16(7), 740; https://doi.org/10.3390/mi16070740 - 25 Jun 2025

Viewed by 759

Abstract

OoC systems employing human cells mirror the functionality of human organs and faithfully simulate their physiological microfluidic environment. Despite the potential of OoC technology in emulating tissue complexity, a significant gap persists in the continuous real-time monitoring of cellular behaviors and their responses [...] Read more.

OoC systems employing human cells mirror the functionality of human organs and faithfully simulate their physiological microfluidic environment. Despite the potential of OoC technology in emulating tissue complexity, a significant gap persists in the continuous real-time monitoring of cellular behaviors and their responses to external stimuli, arising from the lack of biosensors integrated onto OoC microfluidic platforms. Addressing this limitation constitutes the primary objective of this study. By developing and incorporating biosensors onto a modular integrated OoC platform, we aim to enable the monitoring of changes taking place in the cellular environment under various stimuli in real time. An in-series modular integration of a biosensor array into an OoC platform is demonstrated herein, along with its potential to sustain human cell proliferation and accommodate the detection of IL-6, as an example of a mediator protein secreted as part of the immune response to inflammation. The implementation of commercially fabricated PCB components also addresses the issue of cost efficiency and manufacturing scaling-up of sensor-integrated OoCs. This advancement will not only enhance the accuracy and reliability of preclinical studies, but also pave the way for improved drug development and disease treatment. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

► Show Figures

Figure 1

32 pages, 5584 KB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advancements in Metal–Organic Framework-Based Microfluidic Chips for Biomedical Applications

by Alemayehu Kidanemariam and Sungbo Cho

Micromachines 2025, 16(7), 736; https://doi.org/10.3390/mi16070736 - 24 Jun 2025

Cited by 1 | Viewed by 1395

Abstract

The integration of metal–organic frameworks (MOFs) with microfluidic technologies has opened new frontiers in biomedical diagnostics and therapeutics. Microfluidic chips offer precise fluid control, low reagent use, and high-throughput capabilities features further enhanced by MOFs’ ample surface area, adjustable porosity, and catalytic activity. [...] Read more.

The integration of metal–organic frameworks (MOFs) with microfluidic technologies has opened new frontiers in biomedical diagnostics and therapeutics. Microfluidic chips offer precise fluid control, low reagent use, and high-throughput capabilities features further enhanced by MOFs’ ample surface area, adjustable porosity, and catalytic activity. Together, they form powerful lab-on-a-chip platforms for sensitive biosensing, drug delivery, tissue engineering, and microbial detection. This review highlights recent advances in MOF-based microfluidic systems, focusing on material innovations, fabrication methods, and diagnostic applications. Particular emphasis is placed on MOF nanozymes, which enhance biochemical reactions for multiplexed testing and rapid pathogen identification. Challenges such as stability, biocompatibility, and manufacturing scalability are addressed, along with emerging trends like responsive MOFs, AI-assisted design, and clinical translation strategies. By bridging MOF chemistry and microfluidic engineering, these systems hold great promise for next-generation biomedical technologies. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

► Show Figures

Figure 1

16 pages, 3111 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Parametric Rule-Based Intelligent System (PRISM) for Design and Analysis of High-Strength Separable Microneedles

by Sanghwi Ju, Seung-hyun Im, Kyungsun Seo, Junhyeok Lee, Seokjae Kim, Tongil Park, Taeksu Lee, Byungjeon Kang, Jayoung Kim, Ryong Sung, Jong-Oh Park and Doyeon Bang

Micromachines 2025, 16(7), 726; https://doi.org/10.3390/mi16070726 - 21 Jun 2025

Viewed by 593

Abstract

Transdermal microneedle systems have received great attention due to their minimally invasive way of delivering biomolecules through the skin with reduced pain. However, designing high-strength separable microneedles, which enable easy skin penetration and easy patch detachment, is challenging. Here, we present a Parametric [...] Read more.

Transdermal microneedle systems have received great attention due to their minimally invasive way of delivering biomolecules through the skin with reduced pain. However, designing high-strength separable microneedles, which enable easy skin penetration and easy patch detachment, is challenging. Here, we present a Parametric Rule-based Intelligent System (PRISM), which generates the design of and analyzes high-strength separable microneedles. The PRISM platform integrates parametric 3D modeling, geometry-based structural analysis, and high-resolution micro-3D printing for the creation of high-strength separable microneedles. We fabricated prototype microneedle arrays via microscale stereolithographic printing (pµSL) and demonstrated separation of microneedle tips in a skin-mimicking phantom sample. Mechanical testing showed that the suggested design achieved 2.13 ± 0.51 N axial resistance and 73.92 ± 34.77 mN shear fracture force; this surpasses that of conventional designs. Finally, an experiment using a skin-mimicking artificial phantom sample confirmed that only the PRISM-designed separable microneedles could have been inserted and separated at the target depth, whereas conventional designs failed to detach. This approach addresses the development of microneedle systems, which achieve both robust skin phantom penetration and reliable separable delivery, presenting an efficient development tool in transdermal drug delivery technology. Full article

(This article belongs to the Section D3: 3D Printing and Additive Manufacturing)

► Show Figures

Figure 1

15 pages, 2341 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Roll-to-Roll (R2R) High-Throughput Manufacturing of Foil-Based Microfluidic Chips for Neurite Outgrowth Studies

by Nihan Atak, Martin Smolka, Anja Haase, Alexandra Lorenz, Silvia Schobesberger, Stephan Ruttloff, Christian Wolf, Ana Ayerdi-Izquierdo, Peter Ertl, Nerea Briz Iceta, Jan Hesse and Martin Frauenlob

Micromachines 2025, 16(6), 713; https://doi.org/10.3390/mi16060713 - 16 Jun 2025

Viewed by 3132

Abstract

Microfluidic devices have emerged as a pivotal in vitro technology for axon outgrowth studies, facilitating the separation of the cell body from the neurites by geometric constraints. However, traditional microfabrication techniques fall short in terms of scalability for large-scale production, hindering widespread application. [...] Read more.

Microfluidic devices have emerged as a pivotal in vitro technology for axon outgrowth studies, facilitating the separation of the cell body from the neurites by geometric constraints. However, traditional microfabrication techniques fall short in terms of scalability for large-scale production, hindering widespread application. This study presents the development of foil-based cell culture chips, made of polyethylene terephthalate and in-house formulated ultraviolet curable liquid resin by high-throughput roll-to-roll (R2R) manufacturing. Here, two microchannel designs were tested to optimize manufacturing quality and assess the neurite outgrowth behavior. The fabricated neuron-foil chips demonstrated biocompatibility and supported neurite outgrowth within microchannels under static cell culture conditions. Furthermore, fluidic flow, oriented either perpendicular or parallel to the microchannel direction, was applied to enhance the biological reproducibility within the neuron-foil chips. These findings suggest that R2R manufacturing offers a promising approach for the high-throughput production of biocompatible microfluidic devices, advancing their potential application in modeling neurological diseases within the biomedical industry. Full article

(This article belongs to the Section B2: Biofabrication and Tissue Engineering)

► Show Figures

Figure 1

23 pages, 2579 KB

Open AccessFeature PaperEditor’s ChoiceReview

From Micro to Marvel: Unleashing the Full Potential of Click Chemistry with Micromachine Integration

by Zihan Chen, Zimo Ren, Carmine Coluccini and Paolo Coghi

Micromachines 2025, 16(6), 712; https://doi.org/10.3390/mi16060712 - 15 Jun 2025

Viewed by 3427

Abstract

Micromachines, small-scale engineered devices prepared to carry out exact tasks at the micro level, have garnered great interest across different fields such as drug delivery, chemical synthesis, and biomedical applications. In emerging applications, micromachines have indicated great potential in advancing click chemistry, a [...] Read more.

Micromachines, small-scale engineered devices prepared to carry out exact tasks at the micro level, have garnered great interest across different fields such as drug delivery, chemical synthesis, and biomedical applications. In emerging applications, micromachines have indicated great potential in advancing click chemistry, a highly selective and efficient chemical technique widely applied in materials science, bioconjugation, and pharmaceutical development. Click chemistry, distinguished by its rapid reaction rates, high efficiency, and bioorthogonality, serves as a robust method for molecular assembly and functionalization. Incorporating micromachines into click chemistry processes paves the way for precise, automated, and scalable chemical synthesis. These tiny devices can effectively transport reactants, boost reaction efficiency through localized mixing, and enable highly exact site-specific modifications. Moreover, micromachines driven by external forces such as magnetic fields, ultrasound, or chemical fuels provide exceptional control over reaction conditions, significantly enhancing the selectivity and efficiency of click reactions. In this review, we explore the interaction between micromachines and click chemistry, showcasing recent advancements, potential uses, and future prospects in this cross-disciplinary domain. By leveraging micromachine-supported click chemistry, scientists can surpass conventional reaction constraints, opening doors to groundbreaking innovations in materials science, drug discovery, and beyond. Full article

► Show Figures

Figure 1

20 pages, 12065 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Design and Optimization of a Tapered Magnetic Soft Continuum Robot for Enhanced Navigation in Cerebral Vasculature

by Jiahang Wang, Yuhang Liu, Xiwen Lu, Yunlong Zhu and Chenyao Bai

Micromachines 2025, 16(6), 701; https://doi.org/10.3390/mi16060701 - 12 Jun 2025

Viewed by 1123

Abstract

Magnetic soft continuum robots (MSCRs) have broad application advantages in vascular intervention; however, current MSCRs still face challenges in navigating the narrower and tortuous structure of the cerebral vasculature. To address this challenge, we propose a tapered MSCR (T-MSCR), which is designed to [...] Read more.

Magnetic soft continuum robots (MSCRs) have broad application advantages in vascular intervention; however, current MSCRs still face challenges in navigating the narrower and tortuous structure of the cerebral vasculature. To address this challenge, we propose a tapered MSCR (T-MSCR), which is designed to facilitate smooth navigation through microvascular structures via its miniature tip. Specifically, to optimize its bending ability, we combine the Gray Wolf Optimizer (GWO) with the Euler–Bernoulli beam theory and introduce a Discrete GWO (DGWO) approach to optimize the distribution of magnetic particles within the T-MSCR. We then demonstrate the optimization process of the T-MSCR’s bending ability, comparing and analyzing its deflection angle and deformation characteristics, highlighting its capability to enter microvasculars. Furthermore, we demonstrate the magnetic steering and path selection capabilities of T-MSCR in a two-dimensional vascular model and its navigation performance in real-scale human vascular models. Finally, biocompatibility tests confirm that T-MSCR exhibits no toxicity to human cells, thereby laying a solid foundation for its clinical application. The proposed T-MSCR design and optimization are expected to provide a more efficient and feasible solution for future cerebrovascular interventions. Full article

(This article belongs to the Section B：Biology and Biomedicine)

► Show Figures

Figure 1

24 pages, 10324 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Versatile Platform for Designing and Fabricating Multi-Material Perfusable 3D Microvasculatures

by Nathaniel Harris, Charles Miller and Min Zou

Micromachines 2025, 16(6), 691; https://doi.org/10.3390/mi16060691 - 8 Jun 2025

Viewed by 1442

Abstract

Perfusable microvasculature is critical for advancing in vitro tissue models, particularly for neural applications where limited diffusion impairs organoid growth and fails to replicate neurovascular function. This study presents a versatile fabrication platform that integrates mesh-driven design, two-photon lithography (TPL), and modular interfacing [...] Read more.

Perfusable microvasculature is critical for advancing in vitro tissue models, particularly for neural applications where limited diffusion impairs organoid growth and fails to replicate neurovascular function. This study presents a versatile fabrication platform that integrates mesh-driven design, two-photon lithography (TPL), and modular interfacing to create multi-material, perfusable 3D microvasculatures. Various 2D and 3D capillary paths were test-printed using both polygonal and lattice support strategies. A double-layered capillary scaffold based on the Hilbert curve was used for comparative materials testing. Methods for printing rigid (OrmoComp), moderately stiff hydrogel (polyethylene glycol diacrylate, PEGDA 700), and soft elastomeric (photocurable polydimethylsiloxane, PDMS) materials were developed and evaluated. Cone support structures enabled high-fidelity printing of the softer materials. A compact heat-shrink tubing interface provided leak-free perfusion without bulky fittings. Physiologically relevant flow velocities and Dextran diffusion through the scaffold were successfully demonstrated. Cytocompatibility assays confirmed that all TPL-printed scaffold materials supported human neural stem cell viability. Among peripheral components, lids fabricated via fused deposition modeling designed to hold microfluidic needle adapters exhibited good biocompatibility, while those made using liquid crystal display-based photopolymerization showed significant cytotoxicity despite indirect exposure. Overall, this platform enables creation of multi-material microvascular systems facilitated by TPL technology for complex, 3D neurovascular modeling, blood–brain barrier studies, and integration into vascularized organ-on-chip applications. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

► Show Figures

Figure 1

26 pages, 7002 KB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Microfluidic Impedance Detection: Principle, Design and Applications

by Yigang Shen, Zhenxiao Wang, Tingyu Ren, Jianming Wen, Jianping Li and Tao Tang

Micromachines 2025, 16(6), 683; https://doi.org/10.3390/mi16060683 - 5 Jun 2025

Viewed by 1276

Abstract

Under the dual drivers of precision medicine development and health monitoring demands, the development of real-time biosensing technologies has emerged as a key breakthrough in the field of life science analytics. Microfluidic impedance detection technology, achieved through the integration of microscale fluid manipulation [...] Read more.

Under the dual drivers of precision medicine development and health monitoring demands, the development of real-time biosensing technologies has emerged as a key breakthrough in the field of life science analytics. Microfluidic impedance detection technology, achieved through the integration of microscale fluid manipulation and bioimpedance spectrum analysis, has enabled the real-time monitoring of biological samples ranging from single cells to organ-level systems, now standing at the forefront of biological real-time detection research. This review systematically summarizes the core principles of microfluidic impedance detection technology, modeling methods for cell equivalent circuits, system optimization strategies, and recent research advancements in biological detection applications. We first elucidate the fundamental principles of microfluidic impedance detection technologies, followed by a comprehensive analysis of cellular equivalent circuit model construction and microfluidic system design optimization strategies. Subsequently, we categorize applications based on biological sample types, elaborating on respective research progress and existing challenges. This review concludes with prospective insights into future developmental trajectories. We hope this work will provide novel research perspectives for advancing microfluidic impedance detection technology while stimulating interdisciplinary collaboration among researchers in biology, medicine, chemistry, and physics to propel technological innovation collectively. Full article

(This article belongs to the Special Issue Application of Microfluidic Technology in Bioengineering)

► Show Figures

Figure 1

20 pages, 8428 KB

Open AccessFeature PaperEditor’s ChoiceArticle

The Role of Pd-Pt Bimetallic Catalysts in Ethylene Detection by CMOS-MEMS Gas Sensor Dubbed GMOS

by Hanin Ashkar, Sara Stolyarova, Tanya Blank and Yael Nemirovsky

Micromachines 2025, 16(6), 672; https://doi.org/10.3390/mi16060672 - 31 May 2025

Cited by 1 | Viewed by 3050

Abstract

The importance and challenges of ethylene detection based on combustion-type low-cost commercial sensors for agricultural and industrial applications are well-established. This work summarizes the significant progress in ethylene detection based on an innovative Gas Metal Oxide Semiconductor (GMOS) sensor and a new catalytic [...] Read more.

The importance and challenges of ethylene detection based on combustion-type low-cost commercial sensors for agricultural and industrial applications are well-established. This work summarizes the significant progress in ethylene detection based on an innovative Gas Metal Oxide Semiconductor (GMOS) sensor and a new catalytic composition of metallic nanoparticles. The paper presents a study on ethylene and ethanol sensing using a miniature catalytic sensor fabricated by Complementary Metal Oxide Semiconductor–Silicon-on-Insulator–Micro-Electro-Mechanical System (CMOS-SOI-MEMS) technology. The GMOS performance with bimetallic palladium–platinum (Pd-Pt) and monometallic palladium (Pd) and platinum (Pt) catalysts is compared. The synergetic effect of the Pd-Pt catalyst is observed, which is expressed in the shift of combustion reaction ignition to lower catalyst temperatures as well as increased sensitivity compared to monometallic components. The optimal catalysts and their temperature regimes for low and high ethylene concentrations are chosen, resulting in lower power consumption by the sensor. Full article

(This article belongs to the Collection Women in Micromachines)

► Show Figures

Figure 1

16 pages, 13475 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Low Thermal Stress and Instant Efficient Atomization of Narrow Viscous Microfluid Film Using a Paper Strip Located at the Edge of a Surface Acoustic Wave Atomizer

by Yulin Lei, Yusong Li, Jia Ning, Yu Gu, Chenhui Gai, Qinghe Ma, Yizhan Ding, Benzheng Wang and Hong Hu

Micromachines 2025, 16(6), 628; https://doi.org/10.3390/mi16060628 - 27 May 2025

Viewed by 455

Abstract

A traditional SAW (surface acoustic wave) atomizer directly supplies liquid to the surface of the atomized chip through a paper strip located in the path of the acoustic beam, resulting in irregular distribution of the liquid film, which generates an aerosol with an [...] Read more.

A traditional SAW (surface acoustic wave) atomizer directly supplies liquid to the surface of the atomized chip through a paper strip located in the path of the acoustic beam, resulting in irregular distribution of the liquid film, which generates an aerosol with an uneven particle size distribution and poor directional controllability, and a high heating phenomenon that can easily break the chip in the atomization process. This paper presents a novel atomization method: a paper strip located at the edge of the atomizer (PSLEA), which forms a micron-sized narrow liquid film at the junction of the atomization chip edge and the paper strip under the effect of acoustic wetting. By using this method, physical separation of the atomized aerosol and jetting droplets can be achieved at the initial stage of atomizer startup, and an ideal aerosol plume with no jetting of large droplets, a uniform particle size distribution, a vertical and stable atomization direction, and good convergence of the aerosol beam can be quickly formed. Furthermore, the effects of the input power, and different paper strips and liquid supply methods on the atomization performance, as well as the heating generation capacity of the liquid in the atomization zone during the atomization process were explored through a large number of experiments, which highlighted the advantages of PSLEA atomization. The experiments demonstrated that the maximum atomization rate under the PSLEA atomization mode reached 2.6 mL/min initially, and the maximum thermal stress was 45% lower compared with that in the traditional mode. Additionally, a portable handheld atomizer with stable atomization performance and a median aerosol particle size of 3.95 μm was designed based on the proposed PSLEA atomization method, showing the great potential of SAW atomizers in treating respiratory diseases. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

► Show Figures

Figure 1

14 pages, 17404 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Reconfigurable Orbital Electrowetting for Controllable Droplet Transport on Slippery Surfaces

by Jiayao Wu, Huafei Li, Yifan Zhou, Ge Gao, Teng Zhou, Ziyu Wang and Huai Zheng

Micromachines 2025, 16(6), 618; https://doi.org/10.3390/mi16060618 - 25 May 2025

Viewed by 778

Abstract

The controllable transport of droplets on solid surfaces is crucial for many applications, from water harvesting to bio-analysis. Herein, we propose a novel droplet transport controlling method, reconfigurable orbital electrowetting (ROEW) on inclined slippery liquid-infused porous surfaces (SLIPS), which enables controllable transport and [...] Read more.

The controllable transport of droplets on solid surfaces is crucial for many applications, from water harvesting to bio-analysis. Herein, we propose a novel droplet transport controlling method, reconfigurable orbital electrowetting (ROEW) on inclined slippery liquid-infused porous surfaces (SLIPS), which enables controllable transport and dynamic handling of droplets by non-contact reconfiguration of orbital electrodes. The flexible reconfigurability is attributed to the non-contact wettability modulation and reversibly deformable flexible electrodes. ROEW graphically customizes stable wettability pathways by real-time and non-contact printing of charge-orbit patterns on SLIPS to support the continuous transport of droplets. Benefiting from the fast erase-writability of charges and the movability of non-contact electrodes, ROEW enables reconfiguration of the wetting pathways by designing electrode shapes and dynamically switching electrode configurations, achieving controllable transport of various pathways and dynamic handling of droplet sorting and mixing. ROEW provides a new approach for reconfigurable, electrode-free arrays and reusable microfluidics. Full article

(This article belongs to the Topic Micro-Mechatronic Engineering, 2nd Edition)

► Show Figures

Figure 1

20 pages, 4542 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Multifunctional Capsule-like Puncture Biopsy Robot for the Gastrointestinal System

by Xinmiao Xu, Jinghan Gao, Dingwen Tong, Yiqun Zhao, Xinjian Fan and Wanning Ge

Micromachines 2025, 16(5), 589; https://doi.org/10.3390/mi16050589 - 18 May 2025

Viewed by 842

Abstract

Gastrointestinal submucosal tumors (SMTs) are difficult to diagnose accurately due to their deep location and the limitations of traditional biopsy tools. To address these issues, we propose a multifunctional capsule-shaped puncture biopsy robot (PBR) with capabilities for tissue sampling, thermal hemostasis, and multi-stage [...] Read more.

Gastrointestinal submucosal tumors (SMTs) are difficult to diagnose accurately due to their deep location and the limitations of traditional biopsy tools. To address these issues, we propose a multifunctional capsule-shaped puncture biopsy robot (PBR) with capabilities for tissue sampling, thermal hemostasis, and multi-stage drug delivery. The PBR measures 27 mm in length and 13 mm in diameter, integrating a micro-scale electro-permanent magnetic system with a 60-turn dual-layer coil (wire diameter: 0.6 mm) to drive an 8 mm-depth puncture needle. A graphene–carbon nanotube composite heating film enables rapid and safe temperature elevation, achieving effective hemostasis and triggering sequential drug release using paraffin-based phase-change materials. Heating remains within the clinical safety range. Experiments demonstrated successful tissue penetration, precise magnetic control, and reliable staged pigment release simulating drug delivery. Tests on an ex vivo porcine stomach confirmed adaptability to irregular gastric surfaces. This compact PBR provides an integrated and minimally invasive approach to both the diagnosis and treatment of gastrointestinal lesions. Full article

(This article belongs to the Section A：Physics)

► Show Figures

Figure 1

14 pages, 4835 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Development and Evaluation of Multi-Module Retinal Devices for Artificial Vision Applications

by Kuang-Chih Tso, Yoshinori Sunaga, Yuki Nakanishi, Yasuo Terasawa, Makito Haruta, Kiyotaka Sasagawa and Jun Ohta

Micromachines 2025, 16(5), 580; https://doi.org/10.3390/mi16050580 - 15 May 2025

Viewed by 609

Abstract

Artificial retinal devices require a high-density electrode array and mechanical flexibility to effectively stimulate retinal cells. However, designing such devices presents significant challenges, including the need to conform to the curvature of the eyeball and cover a large area using a single platform. [...] Read more.

Artificial retinal devices require a high-density electrode array and mechanical flexibility to effectively stimulate retinal cells. However, designing such devices presents significant challenges, including the need to conform to the curvature of the eyeball and cover a large area using a single platform. To address these issues, we developed a parylene-based multi-module retinal device (MMRD) integrating a complementary metal-oxide semiconductor (CMOS) system. The proposed device is designed for suprachoroidal transretinal stimulation, with each module comprising a parylene-C thin-film substrate, a CMOS chip, and a ceramic substrate housing seven platinum electrodes. The smart CMOS system significantly reduces wiring complexity, enhancing the device’s practicality. To improve fabrication reliability, we optimized the encapsulation process, introduced multiple silane coupling modifications, and utilized polyvinyl alcohol (PVA) for easier detachment in flip-chip bonding. This study demonstrates the fabrication and evaluation of the MMRD through in vitro and in vivo experiments. The device successfully generated the expected current stimulation waveforms in both settings, highlighting its potential as a promising candidate for future artificial vision applications. Full article

(This article belongs to the Section E：Engineering and Technology)

► Show Figures

Figure 1

13 pages, 2446 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Novel Pathogen Detection System Combining a Nucleic Acid Extraction Biochip with a Perovskite Photodetector

by Zhuo Gao, Pan Wang, Chang Chen, Jian Duan, Shilun Feng and Bo Liu

Micromachines 2025, 16(5), 581; https://doi.org/10.3390/mi16050581 - 15 May 2025

Viewed by 2685

Abstract

The increasing spread of infectious diseases caused by pathogenic microorganisms underscores the urgent need for highly sensitive, portable, and rapid nucleic acid detection technologies to facilitate early diagnosis and effective prevention. In this study, we developed a fluorescence-based nucleic acid detection platform that [...] Read more.

The increasing spread of infectious diseases caused by pathogenic microorganisms underscores the urgent need for highly sensitive, portable, and rapid nucleic acid detection technologies to facilitate early diagnosis and effective prevention. In this study, we developed a fluorescence-based nucleic acid detection platform that integrates a microfluidic chip with an all-inorganic perovskite photodetector. The system enables integrated operation of nucleic acid extraction, purification, and amplification on a microfluidic chip, combined with real-time electrical signal readout via a CsPbBr₃ perovskite photodetector. Experimental results indicate that the photodetector exhibits high responsivity at 530 nm, aligning well with the primary emission peak of FAM. The system demonstrates a strong linear correlation between photocurrent and FAM concentration over the range of 0.01–0.4 μM (R² = 0.928), with a low detection limit of 0.01 μM and excellent reproducibility across multiple measurements. Validation using FAM standard solutions and Escherichia coli samples confirmed the system’s reliable linearity and signal stability. This platform demonstrates strong potential for rapid pathogen screening and point-of-care diagnostic applications. Full article

(This article belongs to the Special Issue Recent Progress of Lab-on-a-Chip Assays)

► Show Figures

Figure 1

46 pages, 6940 KB

Open AccessFeature PaperEditor’s ChoiceReview

High-Performance Carbon Nanotube Electronic Devices: Progress and Challenges

by Zirui Zhang, Nie Zhang and Zhiyong Zhang

Micromachines 2025, 16(5), 554; https://doi.org/10.3390/mi16050554 - 1 May 2025

Cited by 3 | Viewed by 3277

Abstract

As silicon-based complementary metal-oxide-semiconductor (CMOS) technology approaches its physical and scaling limits at sub-3-nanometer nodes, critical challenges including the short-channel effect (SCE), surging power consumption, and aggravated parasitic effects have severely constrained further improvements in device performance, integration density, and energy efficiency. Carbon [...] Read more.

As silicon-based complementary metal-oxide-semiconductor (CMOS) technology approaches its physical and scaling limits at sub-3-nanometer nodes, critical challenges including the short-channel effect (SCE), surging power consumption, and aggravated parasitic effects have severely constrained further improvements in device performance, integration density, and energy efficiency. Carbon nanotubes (CNTs), with their superior electrical properties, exceptional gate controllability enabled by one-dimensional nanostructure, and compatibility with existing semiconductor processes, have emerged as an ideal candidate material for post-silicon high-performance electronics. Since their discovery, CNT electronics have evolved from fundamental research to a comprehensive technological framework. This review first systematically elaborates the physical characteristics of CNTs and operation mechanisms of electronic devices. Subsequently, we comprehensively summarize recent research progress in high-performance CNT electronic devices with particular emphasis on their breakthrough achievements. Through critical analysis of current developments, we thoroughly discuss fundamental challenges in material synthesis, device fabrication, and circuit integration, while evaluating potential solutions. Finally, we concentrate on future development directions for high-performance CNT devices, aiming to call for collaborative efforts from both academia and industry to accelerate the transition of CNT electronics from laboratory research to industrial implementation. Full article

(This article belongs to the Special Issue Multifunctional Transistors: Outlooks and Challenges)

► Show Figures

Figure 1

20 pages, 2666 KB

Open AccessFeature PaperEditor’s ChoiceReview

Development of Energy-Selective Surface for Electromagnetic Protection

by Jinghao Lv, Caofei Luo, Jiwei Zhao, Haoran Han, Huan Lu and Bin Zheng

Micromachines 2025, 16(5), 555; https://doi.org/10.3390/mi16050555 - 1 May 2025

Cited by 1 | Viewed by 774

Abstract

Energy-selective surfaces (ESSs) have gained attention as an advanced electromagnetic protection technology. This review discusses the evolution of ESSs, focusing on four key areas: frequency bandwidth expansion, material innovations, functional enhancements, and application diversification. ESSs have evolved from narrowband designs to providing ultra-wideband [...] Read more.

Energy-selective surfaces (ESSs) have gained attention as an advanced electromagnetic protection technology. This review discusses the evolution of ESSs, focusing on four key areas: frequency bandwidth expansion, material innovations, functional enhancements, and application diversification. ESSs have evolved from narrowband designs to providing ultra-wideband protection, covering L-band to K-band frequencies. New designs, including non-reciprocal mechanisms and cascaded filters, enhance the shielding efficiency. Material advancements like the use of vanadium dioxide (VO₂) and micro–nano fabrication techniques have reduced costs and improved performance, enabling higher-frequency applications. Future developments aim to overcome the current limitations, offering a broader bandwidth, higher power tolerance, and faster response times. ESSs play a key role in integrated electromagnetic protection systems. Full article

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

► Show Figures

Figure 1

9 pages, 13670 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Ultra-Short-Pulse Laser Welding of Glass to Metal with a Shear Strength Above 50 MPa

by Lukas Günther, Jens Ulrich Thomas, Jens Hermann, Axel Ohlinger and Dominique de Ligny

Micromachines 2025, 16(5), 538; https://doi.org/10.3390/mi16050538 - 30 Apr 2025

Cited by 1 | Viewed by 879

Abstract

We report an ultra-short-pulse laser welding process that allows one to consistently weld Borofloat^® 33 glass to aluminum with a shear strength above 50 MPa. We explored the morphology of the welding seam and quantified the quality of the bonding by statistically [...] Read more.

We report an ultra-short-pulse laser welding process that allows one to consistently weld Borofloat^® 33 glass to aluminum with a shear strength above 50 MPa. We explored the morphology of the welding seam and quantified the quality of the bonding by statistically determining the shear strength with more than 30 samples. The results of the shear strength tests indicate that the intrinsic shear strength of the aluminum serves as the upper limit of the glass-to-metal bond. Full article

(This article belongs to the Special Issue Advancement of Laser Technology from Materials Processing to Nano/Micro Fabrications)

► Show Figures

Figure 1

19 pages, 1093 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Rheological Property Changes in Polyacrylamide Aqueous Solution Flowed Through Microchannel Under Low Reynolds Number and High Shear Rate Conditions

by Yishuai Li, Yukihiro Yonemoto, Yuki Yamahata and Akimaro Kawahara

Micromachines 2025, 16(5), 545; https://doi.org/10.3390/mi16050545 - 30 Apr 2025

Viewed by 518

Abstract

As an important structure of microfluidic devices, microchannels have the advantages of precise flow control and high reaction efficiency. This study investigates experimentally changing the rheological properties of a polyacrylamide (PAM) aqueous solution after flowing through a square microchannel with a hydraulic diameter [...] Read more.

As an important structure of microfluidic devices, microchannels have the advantages of precise flow control and high reaction efficiency. This study investigates experimentally changing the rheological properties of a polyacrylamide (PAM) aqueous solution after flowing through a square microchannel with a hydraulic diameter of 0.5 mm under low Reynolds number and high shear rate conditions. To know the effect of the channel length on the change in viscosity and relaxation time, the length is changed to 100 mm and 200 mm. From the experiment, it is found that both the viscosity and relaxation time of the solution decrease with increasing the shear rate and the microchannel length. Based on the present experimental data, an empirical model is proposed to predict the change ratio of the relaxation time before and after passing through the microchannel, and the calculation with the model has an agreement with the experiment with root-mean-square absolute error of 0.007. Full article

(This article belongs to the Special Issue Flows in Micro- and Nano-Systems)

► Show Figures

Figure 1

15 pages, 2084 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Characterization of the Coating Layers Deposited onto Curved Surfaces Using a Novel Multi-Nozzle Extrusion Printer

by Ramses Seferino Trigo Torres, Lawrence Kulinsky and Arash Kheradvar

Micromachines 2025, 16(5), 505; https://doi.org/10.3390/mi16050505 - 26 Apr 2025

Viewed by 579

Abstract

Over the past two decades, additive manufacturing has advanced significantly, enabling rapid fabrication of functional components across various applications. In medical devices, it has been used for prototyping, prosthetics, drug delivery platforms, and more recently, tissue scaffolding. However, current technologies face challenges, particularly [...] Read more.

Over the past two decades, additive manufacturing has advanced significantly, enabling rapid fabrication of functional components across various applications. In medical devices, it has been used for prototyping, prosthetics, drug delivery platforms, and more recently, tissue scaffolding. However, current technologies face challenges, particularly in depositing conformal layers over curved surfaces. This study introduces a novel multi-nozzle extrusion printer concept designed to deposit soft gel layers onto curved surfaces. A custom clearance locking mechanism enhances the printer’s ability to achieve conformal coatings on both flat and curved substrates. We investigate key deposition parameters, including displacement volume and nozzle configuration, while comparing two deposition sequences: “Press and Express” and “Express and Press”. Our results demonstrate that the “Express and Press” technique yields more uniform, merged conformal layers than the “Press and Express” method. This technology holds promise for further refinement and potential applications in tissue engineering. Full article

(This article belongs to the Section B2: Biofabrication and Tissue Engineering)

► Show Figures

Figure 1

15 pages, 2921 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Application of Inertial Microfluidics for Isolation and Removal of Round Spermatids from a Spermatogenic Cell Sample to Assist In-Vitro Human Spermatogenesis

by Sabin Nepal, Joey Casalini, Alex Jafek and Bruce Gale

Micromachines 2025, 16(5), 500; https://doi.org/10.3390/mi16050500 - 25 Apr 2025

Viewed by 640

Abstract

In-vitro spermatogenesis holds great potential in addressing male infertility, yet one of the main challenges is separating round spermatids from other germ cells in spermatogonial stem cell cultures. STA-PUT, a method based on velocity sedimentation, has been extensively tested for this application. Though [...] Read more.

In-vitro spermatogenesis holds great potential in addressing male infertility, yet one of the main challenges is separating round spermatids from other germ cells in spermatogonial stem cell cultures. STA-PUT, a method based on velocity sedimentation, has been extensively tested for this application. Though somewhat effective, it requires bulky, expensive equipment and significant time. In contrast, the method of inertial microfluidics offers a compact, cost-effective, and faster alternative. In this study, we designed, fabricated, and tested a microfluidic spiral channel for isolating round spermatids and purifying spermatogenic cells. A commercially available spiral device close to the calculated specifications was tested for rapid prototyping, achieving 79% purity for non-spermatid cells in a single pass, with ability to achieve higher purity through repeated passes. However, the commercial device’s narrow outlets caused clogging, prompting the fabrication of a custom polydimethylsiloxane device matching the calculated specifications. This custom device demonstrated significant improvements, achieving 86% purity in a single pass compared to STA-PUT’s 38%, and that without any clogging issues. Further purification could be attained by repeated passes, as shown in earlier studies. This work underscores the efficacy of inertial microfluidics for efficient, high-purity cell separation, with the potential to revolutionize workflows in in-vitro spermatogenesis research. Full article

(This article belongs to the Special Issue Application of Microfluidic Technology in Biology)

► Show Figures

Figure 1

15 pages, 13926 KB

Open AccessFeature PaperEditor’s ChoiceArticle

High-Temperature Properties of LP-DED Additive Manufactured Ferritic STS 430 Deposits on Martensitic STS 410 Base Metal

by Samsub Byun, Hyun-Ki Kang, Namhyun Kang and Seunghun Lee

Micromachines 2025, 16(5), 494; https://doi.org/10.3390/mi16050494 - 23 Apr 2025

Cited by 1 | Viewed by 650

Abstract

The aim of this work is to study the phase transformations, microstructures, and mechanical properties of ferritic stainless steel (FSS) 430 deposits on martensitic stainless steel (MSS) 410 base metal (BM) using laser powder-directed energy deposition (LP-DED) additive manufacturing. The LP-DED additive manufactured [...] Read more.

The aim of this work is to study the phase transformations, microstructures, and mechanical properties of ferritic stainless steel (FSS) 430 deposits on martensitic stainless steel (MSS) 410 base metal (BM) using laser powder-directed energy deposition (LP-DED) additive manufacturing. The LP-DED additive manufactured FSS 430 deposits on MSS 410 BM underwent post-heat treatment at 815 °C and 980 °C for 1 h, respectively. The analyses of phase transformations and microstructural evolutions of LP-DED FSS 430 on MSS 410 BM were carried out using X-ray diffraction, SEM, and EBSD. The highest strain was observed at the coarsened chromium carbide (Cr₂₃C₆) in the joint interface between AM FSS 430 and MSS 410 MB. This contributed to localized lattice distortion and mismatch in crystal structure between chromium carbide and the surrounding ferrite. Tensile strength properties at elevated temperatures were discussed to investigate the effects of the different post-heat treatments. The tensile properties of the as-built samples including tensile strength of about 550 MPa and elongation of about 20%, were the same as those of the commercial FSS 430 material. Tensile properties at 500 °C indicated a modest increase in tensile strength to 540–550 MPa. The specimens heat treated at 980 °C retained higher tensile strength than those heat treated at 815 °C. This would be attributed to the grain refinement from prior LP-DED microstructure and chromium carbide coarsening at higher heat treatment, which can increase dislocation density and yield harder mechanical behavior. Full article

(This article belongs to the Special Issue Laser Additive Manufacturing of Metallic Materials, 2nd Edition)

► Show Figures

Figure 1

17 pages, 9262 KB

Open AccessEditor’s ChoiceArticle

Infrared Absorption of Laser Patterned Sapphire Al₂O₃ for Radiative Cooling

by Nan Zheng, Daniel Smith, Soon Hock Ng, Hsin-Hui Huang, Dominyka Stonytė, Dominique Appadoo, Jitraporn Vongsvivut, Tomas Katkus, Nguyen Hoai An Le, Haoran Mu, Yoshiaki Nishijima, Lina Grineviciute and Saulius Juodkazis

Micromachines 2025, 16(4), 476; https://doi.org/10.3390/mi16040476 - 16 Apr 2025

Cited by 1 | Viewed by 1043

Abstract

The reflectance (R) of linear and circular micro-gratings on c-plane sapphire Al₂O₃ ablated by a femtosecond (fs) laser were spectrally characterised for thermal emission

\propto (1 - R)

in the mid-to-far infrared (IR) spectral range. An [...] Read more.

The reflectance (R) of linear and circular micro-gratings on c-plane sapphire Al₂O₃ ablated by a femtosecond (fs) laser were spectrally characterised for thermal emission

\propto (1 - R)

in the mid-to-far infrared (IR) spectral range. An IR camera was used to determine the blackbody radiation temperature from laser-patterned regions, which showed (3–6)% larger emissivity dependent on the grating pattern. The azimuthal emission curve closely followed the Lambertian angular profile

\propto cos θ_{a}

at the 7.5–13 μm emission band. The back-side ablation method on transparent substrates was employed to prevent debris formation during energy deposition as it applies a forward pressure of >0.3 GPa to the debris and molten skin layer. The back-side ablation maximises energy deposition at the exit interface where the transition occurs from the high-to-low refractive index. Phononic absorption in the Reststrahlen region 20–30 μm can be tailored with the fs laser inscription of sensor structures/gratings. Full article

► Show Figures

Figure 1

15 pages, 6112 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Study on the Mechanism of the Micro-Charge-Detonation-Driven Flyer

by Shuang Li, Jie Ren, Chang Leng, Zhenhao Shi, Yan Ma, Mingyu Li and Qingxuan Zeng

Micromachines 2025, 16(4), 441; https://doi.org/10.3390/mi16040441 - 9 Apr 2025

Viewed by 404

Abstract

To investigate the energy transfer mechanisms during the micro-explosive initiator-driven flyer process and to guide the performance evaluation of micro-sized charges and the structural design of micro-initiators, a combined approach of numerical simulations and experimental tests was employed to study the detonation process [...] Read more.

To investigate the energy transfer mechanisms during the micro-explosive initiator-driven flyer process and to guide the performance evaluation of micro-sized charges and the structural design of micro-initiators, a combined approach of numerical simulations and experimental tests was employed to study the detonation process of copper-based azide micro-charges driving a flyer. The output pressure and detonation velocity of the copper-based azide micro-charge were measured using the manganese–copper piezoresistive method and electrical probe technique, and the corresponding JWL equation of the state parameters was subsequently fitted. A simulation model for the micro-charge-driven flyer was established and validated using Photonic Doppler Velocimetry (PDV), and the influence of charge conditions, structural parameters, and other factors on the flyer velocity and morphology was investigated. The results indicate that the flyer velocity decreases as its thickness increases, whereas the specific kinetic energy of the flyer initially increases and then decreases with increasing thickness. The optimal flyer thickness was found to be in the range of 30 to 70 μm. The flyer velocity increases with the density and height of the micro-charge; however, when the micro-charge density exceeds a certain threshold, the flyer velocity decreases. The flyer velocity exhibits an exponential decline as the diameter of the acceleration chamber increases, whereas it shows a slight increase with the increase in the length of the acceleration chamber. The diameter of the acceleration chamber should not exceed the charge diameter and must be no smaller than the critical diameter required for detonation initiation of the underlying charge. The use of a multi-layer accelerating chamber structure leads to a slight reduction in flyer velocity and further increases in the transmission hole diameter while having no significant impact on the flyer velocity. Full article

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

► Show Figures

Figure 1

18 pages, 3245 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrical Phenotyping of Aged Human Mesenchymal Stem Cells Using Dielectrophoresis

by Lexi L. C. Simpkins, Tunglin Tsai, Emmanuel Egun and Tayloria N. G. Adams

Micromachines 2025, 16(4), 435; https://doi.org/10.3390/mi16040435 - 3 Apr 2025

Cited by 1 | Viewed by 699

Abstract

Human mesenchymal stem cells (hMSCs) are widely used in regenerative medicine, but large-scale in vitro expansion alters their function, impacting proliferation and differentiation potential. Currently, a predictive marker to assess these changes is lacking. Here, we used dielectrophoresis (DEP) to characterize the electrical [...] Read more.

Human mesenchymal stem cells (hMSCs) are widely used in regenerative medicine, but large-scale in vitro expansion alters their function, impacting proliferation and differentiation potential. Currently, a predictive marker to assess these changes is lacking. Here, we used dielectrophoresis (DEP) to characterize the electrical phenotype of hMSCs derived from bone marrow (BM), adipose tissue (AT), and umbilical cord (UC) as they aged in vitro from passage 4 (P4) to passage 9 (P9). The electrical phenotype was defined by the DEP spectra, membrane capacitance, and cytoplasm conductivity. Cell morphology and size, growth characteristics, adipogenic differentiation potential, and osteogenic differentiation potential were assessed alongside label-free biomarker membrane capacitance and cytoplasm conductivity. Differentiation was confirmed by histological staining and RT-qPCR. All hMSCs exhibited typical morphology, though cell size varied, with UC-hMSCs displaying the largest variability across all size metrics. Growth analysis revealed that UC-hMSCs proliferated the fastest. The electrical phenotype varied with cell source and in vitro age, with high passage hMSCs showing noticeable shifts in DEP spectra, membrane capacitance, and cytoplasm conductivity. Correlation analysis revealed that population doubling level (PDL) correlated with membrane capacitance and cytoplasm conductivity, indicating PDL as a more precise marker of in vitro aging than passage number. Additionally, we demonstrate that membrane capacitance correlates with the osteogenic marker COL1A1 and that cytoplasm conductivity correlates with the adipogenic markers ADIPOQ and FABP4, suggesting that DEP-derived electrical properties serve as label-free biomarkers of differentiation potential. While DEP has previously been applied to BM-hMSCs and AT-hMSCs, and more recently to UC-hMSCs, few studies have provided a direct comparison across all three sources or tracked changes across continuous expansion. These findings underscore the utility of DEP as a label-free approach for assessing hMSC aging and function, offering practical applications for optimizing stem cell expansion and stem cell banking in clinical settings. Full article

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

► Show Figures

Figure 1

16 pages, 11832 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Multi-Nozzles 3D Bioprinting Collagen/Thermoplastic Elasto-Mer Scaffold with Interconnect Pores

by Kuo Yao, Kai Guo, Heran Wang and Xiongfei Zheng

Micromachines 2025, 16(4), 429; https://doi.org/10.3390/mi16040429 - 2 Apr 2025

Cited by 1 | Viewed by 1165

Abstract

Scaffolds play a crucial role in tissue engineering as regenerative templates. Fabricating scaffolds with good biocompatibility and appropriate mechanical properties remains a major challenge in this field. This study proposes a method for preparing multi-material scaffolds, enabling the 3D printing of collagen and [...] Read more.

Scaffolds play a crucial role in tissue engineering as regenerative templates. Fabricating scaffolds with good biocompatibility and appropriate mechanical properties remains a major challenge in this field. This study proposes a method for preparing multi-material scaffolds, enabling the 3D printing of collagen and thermoplastic elastomers at room temperature. Addressing the previous challenges such as the poor printability of pure collagen and the difficulty of maintaining structural integrity during multilayer printing, this research improved the printability of collagen by optimizing its concentration and pH value and completed the large-span printing of thermoplastic elastomer using a precise temperature-control system. The developed hybrid scaffold has an interconnected porous structure, which can support the adhesion and proliferation of fibroblasts. The scaffolds were further treated with different post-treatment methods, and it was proven that the neutralized and cross-linked collagen scaffold, which has both nano-fibers and a certain rigidity, can better support the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The research results show that the collagen thermoplastic elastomer hybrid scaffold has significant clinical application potential in soft tissue and hard tissue regeneration, providing a versatile solution to meet the diverse needs of tissue engineering. Full article

(This article belongs to the Section B2: Biofabrication and Tissue Engineering)

► Show Figures

Figure 1

35 pages, 2334 KB

Open AccessFeature PaperEditor’s ChoiceReview

Innovative Micro- and Nano-Architectures in Biomedical Engineering for Therapeutic and Diagnostic Applications

by Nargish Parvin, Sang Woo Joo, Jae Hak Jung and Tapas K. Mandal

Micromachines 2025, 16(4), 419; https://doi.org/10.3390/mi16040419 - 31 Mar 2025

Cited by 2 | Viewed by 1781

Abstract

The rapid evolution of micro- and nano-architectures is revolutionizing biomedical engineering, particularly in the fields of therapeutic and diagnostic micromechanics. This review explores the recent innovations in micro- and nanostructured materials and their transformative impact on healthcare applications, ranging from drug delivery and [...] Read more.

The rapid evolution of micro- and nano-architectures is revolutionizing biomedical engineering, particularly in the fields of therapeutic and diagnostic micromechanics. This review explores the recent innovations in micro- and nanostructured materials and their transformative impact on healthcare applications, ranging from drug delivery and tissue engineering to biosensing and diagnostics. Key advances in fabrication techniques, such as lithography, 3D printing, and self-assembly, have enabled unprecedented control over material properties and functionalities at microscopic scales. These engineered architectures offer enhanced precision in targeting and controlled release in drug delivery, foster cellular interactions in tissue engineering, and improve sensitivity and specificity in diagnostic devices. We examine critical design parameters, including biocompatibility, mechanical resilience, and scalability, which influence their clinical efficacy and long-term stability. This review also highlights the translational potential and current limitations in bringing these materials from the laboratory research to practical applications. By providing a comprehensive overview of the current trends, challenges, and future perspectives, this article aims to inform and inspire further development in micro- and nano-architectures that hold promise for advancing personalized and precision medicine. Full article

(This article belongs to the Special Issue Emerging Trends in Biosensors and Biomolecular Electronics Towards Disease Progression and Treatment)

► Show Figures

Figure 1

27 pages, 2399 KB

Open AccessFeature PaperEditor’s ChoiceReview

Carbon Materials in Voltammetry: An Overview of Versatile Platforms for Antidepressant Drug Detection

by Joanna Smajdor, Katarzyna Fendrych and Anna Górska-Ratusznik

Micromachines 2025, 16(4), 423; https://doi.org/10.3390/mi16040423 - 31 Mar 2025

Viewed by 963

Abstract

This review concentrates on the application of carbon-based materials in the development and fabrication of voltammetric sensors of antidepressant drugs used in the treatment of moderate to severe depression, anxiety disorders, personality disorders, and various phobias. Voltammetric techniques offer outstanding sensitivity and selectivity, [...] Read more.

This review concentrates on the application of carbon-based materials in the development and fabrication of voltammetric sensors of antidepressant drugs used in the treatment of moderate to severe depression, anxiety disorders, personality disorders, and various phobias. Voltammetric techniques offer outstanding sensitivity and selectivity, accuracy, low detection limit, high reproducibility, instrumental simplicity, cost-effectiveness, and short time of direct determination of antidepressant drugs in pharmaceutical and clinical samples. Moreover, the combination of voltammetric approaches with the unique characteristics of carbon and its derivatives has led to the development of powerful electrochemical sensing tools for detecting antidepressant drugs, which are highly desirable in healthcare, environmental monitoring, and the pharmaceutical industry. In this review, carbon-based materials, such as glassy carbon and boron-doped diamond, and a wide spectrum of carbon nanoparticles, including graphene, graphene oxides, reduced graphene oxides, single-walled carbon nanotubes, and multi-walled carbon nanotubes were described in terms of the sensing performance of agomelatine, alprazolam, amitriptyline, aripiprazole, carbamazepine, citalopram, clomipramine, clozapine, clonazepam, desipramine, desvenlafaxine, doxepin, duloxetine, flunitrazepam, fluoxetine, fluvoxamine, imipramine, nifedipine, olanzapine, opipramol, paroxetine, quetiapine, serotonin, sertraline, sulpiride, thioridazine, trazodone, venlafaxine, and vortioxetine. Full article

(This article belongs to the Special Issue Micro- and Nanosensors: Fabrication, Applications and Performance Enhancements, Third Edition)

► Show Figures

Figure 1

14 pages, 4861 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Pico-Scale Digital PCR on a Super-Hydrophilic Microarray Chip for Multi-Target Detection

by Qingyue Xian, Jie Zhang, Yu Ching Wong, Yibo Gao, Qi Song, Na Xu and Weijia Wen

Micromachines 2025, 16(4), 407; https://doi.org/10.3390/mi16040407 - 30 Mar 2025

Viewed by 2763

Abstract

The technology of digital polymerase chain reaction (dPCR) is rapidly evolving, yet current devices often suffer from bulkiness and cumbersome sample-loading procedures. Moreover, challenges such as droplet merging and partition size limitations impede efficiency. In this study, we present a super-hydrophilic microarray chip [...] Read more.

The technology of digital polymerase chain reaction (dPCR) is rapidly evolving, yet current devices often suffer from bulkiness and cumbersome sample-loading procedures. Moreover, challenges such as droplet merging and partition size limitations impede efficiency. In this study, we present a super-hydrophilic microarray chip specifically designed for dPCR, featuring streamlined loading methods compatible with micro-electro-mechanical systems (MEMS) technology. Utilizing hydrodynamic principles, our platform enables the formation of a uniform array of 120-pL independent reaction units within a closed channel. The setup allows for rapid reactions facilitated by an efficient thermal cycler and real-time imaging. We achieved absolute quantitative detection of hepatitis B virus (HBV) plasmids at varying concentrations, alongside multiple targets, including cancer mutation gene fragments and reference genes. This work highlights the chip’s versatility and potential applications in point-of-care testing (POCT) for cancer diagnostics. Full article

(This article belongs to the Special Issue Application of Microfluidic Technology in Bioengineering)

► Show Figures

Figure 1

20 pages, 18426 KB

Open AccessFeature PaperEditor’s ChoiceReview

Nanostructures and Nanomaterials Integrated into Triboelectric Nanogenerators

by Shujie Yang, Victor Klinkov, Natalia Grozova, Svetlana Shalnova, Tatiana Larionova, Oleg Tolochko and Olga Klimova-Korsmik

Micromachines 2025, 16(4), 403; https://doi.org/10.3390/mi16040403 - 29 Mar 2025

Cited by 2 | Viewed by 694

Abstract

The pursuit of eco-friendly and renewable power generation has driven technological breakthroughs in nanoscale engineering, particularly regarding triboelectric nanogenerators (TENGs). These devices have become a focus of interest due to their capacity to effectively transform kinetic energy into electrical power via combined triboelectrification [...] Read more.

The pursuit of eco-friendly and renewable power generation has driven technological breakthroughs in nanoscale engineering, particularly regarding triboelectric nanogenerators (TENGs). These devices have become a focus of interest due to their capacity to effectively transform kinetic energy into electrical power via combined triboelectrification and electrostatic charge separation mechanisms. TENGs now find expanding implementations across multiple fields including in flexible electronics, autonomous sensing systems, and ambient energy conversion technologies. Enhancing TENG performance critically depends on the strategic design and application of nanostructures and nanomaterials. Nonetheless, challenges such as material selection, compatibility, homogeneous dispersion, interfacial stability, and production scalability must be overcome to advance TENG technology. Moreover, the mechanisms by which nanomaterials contribute to the triboelectric effect remain insufficiently understood, underscoring the necessity for systematic theoretical models. This review provides a comprehensive overview of recent advancements in integrating nanostructures and nanomaterials into TENGs, elucidating their roles, advantages, and underlying mechanisms in enhancing energy conversion efficiency, while identifying key challenges and proposing future research directions. Full article

► Show Figures

Figure 1

10 pages, 3122 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Low-Frequency Magnetic Sensing Using Magnetically Modulated Microcavity Resonant Mode

by Xinrong Yang, Jiamin Rong, Enbo Xing, Jianglong Li, Yujie Zhang, Yanru Zhou, Wenyao Liu, Huanfei Wen, Jun Tang and Jun Liu

Micromachines 2025, 16(4), 405; https://doi.org/10.3390/mi16040405 - 29 Mar 2025

Viewed by 507

Abstract

We propose a low-frequency magnetic sensing method using a magnetically modulated microcavity resonant mode. Our magnetically sensitive unit with periodically changing magnetic poles is formed by combining an AC excitation coil with a microcavity. The microcavity vibrates at the frequency of the AC [...] Read more.

We propose a low-frequency magnetic sensing method using a magnetically modulated microcavity resonant mode. Our magnetically sensitive unit with periodically changing magnetic poles is formed by combining an AC excitation coil with a microcavity. The microcavity vibrates at the frequency of the AC amplitude-modulated signal and changes its resonant mode when the sensing unit interacts with a low-frequency magnetic field. Signal processing is performed on the resonant spectrum to obtain low-frequency magnetic signals. The results of the experiment show that the measured sensitivity to a 0.5 Hz magnetic field is 12.49 V/mT, and a bias instability noise of 16.71 nT is achieved. We have extended the measurable frequency range of the whispering gallery mode microcavity magnetometer and presented a development in microcavity magnetic sensing and optical readout. Full article

(This article belongs to the Special Issue The Next Generation of Magnetometer Microsystems and Applications, 2nd Edition)

► Show Figures

Figure 1

14 pages, 3129 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Acoustic Bubbles as Small-Scale Energy Harvesters for Implantable Medical Devices

by Wenbo Li, Anthony Mercader and Sung Kwon Cho

Micromachines 2025, 16(4), 362; https://doi.org/10.3390/mi16040362 - 21 Mar 2025

Viewed by 657

Abstract

Piezoelectric acoustic energy harvesting within the human body has traditionally faced challenges due to insufficient energy levels for biomedical applications. Existing acoustic resonators are often much larger in size, making them impractical for microscale applications. This study investigates the use of acoustically oscillated [...] Read more.

Piezoelectric acoustic energy harvesting within the human body has traditionally faced challenges due to insufficient energy levels for biomedical applications. Existing acoustic resonators are often much larger in size, making them impractical for microscale applications. This study investigates the use of acoustically oscillated microbubbles as energy-harvesting resonators. A comparative study was conducted to determine the energy harvested by a freestanding diaphragm and a diaphragm coupled with an oscillating microbubble. The experimental results demonstrated that incorporating a microbubble enabled the flexible piezoelectric diaphragm to harvest seven times more energy than the freestanding diaphragm. These findings were further validated using Laser Doppler Vibrometer (LDV) measurements and stress calculations. Additional experiments with a phantom tissue tank confirmed the feasibility of this technology for biomedical applications. The results indicate that acoustically resonating microbubbles are a promising design for microscale acoustic energy-harvesting resonators in implantable biomedical devices. Full article

(This article belongs to the Special Issue Micro-/Nanofluidic and Lab-on-a-Chip Devices for Biomedical Applications, 3rd Edition)

► Show Figures

Figure 1

13 pages, 10049 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Rapid and Sensitive Detection of Thrombospondin-2 Using Nanoparticle Sensors for Cancer Screening and Prognosis

by Maziyar Kalateh Mohammadi, Seyedsina Mirjalili, Md Ashif Ikbal, Hao Xie and Chao Wang

Micromachines 2025, 16(3), 354; https://doi.org/10.3390/mi16030354 - 20 Mar 2025

Viewed by 1511

Abstract

Thrombospondin-2 (THBS2) is a prevailing prognostic biomarker implicated in different cancer types, such as deadly colorectal, pancreas, and triple-negative breast cancers. While the current methods for cancer-relevant protein detection, such as enzyme-linked immunosorbent assay (ELISA), mass spectrometry, and immunohistochemistry, are feasible at advanced [...] Read more.

Thrombospondin-2 (THBS2) is a prevailing prognostic biomarker implicated in different cancer types, such as deadly colorectal, pancreas, and triple-negative breast cancers. While the current methods for cancer-relevant protein detection, such as enzyme-linked immunosorbent assay (ELISA), mass spectrometry, and immunohistochemistry, are feasible at advanced stages, they have shortcomings in sensitivity, specificity, and accessibility, particularly at low concentrations in complex biological fluids for early detection. Here, we propose and demonstrate a modular, in-solution assay design concept, Nanoparticle-Supported Rapid Electronic Detection (NasRED), as a versatile cancer screening and diagnostic platform. NasRED utilizes antibody-functionalized gold nanoparticles (AuNPs) to capture target proteins from a minute amount of sample (<10 µL) and achieve optimal performance with a short assay time by introducing active fluidic forces that act to promote biochemical reaction and accelerate signal transduction. This rapid (15 min) process serves to form AuNP clusters upon THBS2 binding and subsequently precipitate such clusters, resulting in color modulation of the test tubes that is dependent on the THBS2 concentration. Finally, a semiconductor-based, portable electronic device is used to digitize the optical signals for the sensitive detection of THBS2. High sensitivity (femtomolar level) and a large dynamic range (five orders of magnitude) are obtained to analyze THBS2 spiked in PBS, serum, whole blood, saliva, cerebrospinal fluids, and synovial fluids. High specificity is also preserved in differentiating THBS2 from other markers such as cancer antigen (CA) 19-9 and bovine serum albumin (BSA). This study highlights NasRED’s potential to enhance cancer prognosis and screening by offering a cost-effective, accessible, and minimally invasive solution. Full article

(This article belongs to the Special Issue Immunoassay Platforms for Biomedical Detection)

► Show Figures

Figure 1

16 pages, 3503 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Modular, Cost-Effective, and Pumpless Perfusion Assembly for the Long-Term Culture of Engineered Microvessels

by Shashwat S. Agarwal, Jacob C. Holter, Travis H. Jones, Brendan T. Fuller, Joseph W. Tinapple, Joseph M. Barlage and Jonathan W. Song

Micromachines 2025, 16(3), 351; https://doi.org/10.3390/mi16030351 - 19 Mar 2025

Viewed by 3161

Abstract

Continuous perfusion is necessary to sustain microphysiological systems and other microfluidic cell cultures. However, most of the established microfluidic perfusion systems, such as syringe pumps, peristaltic pumps, and rocker plates, have several operational challenges and may be cost-prohibitive, especially for laboratories with no [...] Read more.

Continuous perfusion is necessary to sustain microphysiological systems and other microfluidic cell cultures. However, most of the established microfluidic perfusion systems, such as syringe pumps, peristaltic pumps, and rocker plates, have several operational challenges and may be cost-prohibitive, especially for laboratories with no microsystems engineering expertise. Here, we address the need for a cost-efficient, easy-to-implement, and reliable microfluidic perfusion system. Our solution is a modular pumpless perfusion assembly (PPA), which is constructed from commercially available, interchangeable, and aseptically packaged syringes and syringe filters. The total cost for the components of each assembled PPA is USD 1–2. The PPA retains the simplicity of gravity-based pumpless flow systems but incorporates high resistance filters that enable slow and sustained flow for extended periods of time (hours to days). The perfusion characteristics of the PPA were determined by theoretical calculations of the total hydraulic resistance of the assembly and experimental characterization of specific filter resistances. We demonstrated that the PPA enabled reliable long-term culture of engineered endothelialized 3-D microvessels for several weeks. Taken together, our novel PPA solution is simply constructed from extremely low-cost and commercially available laboratory supplies and facilitates robust cell culture and compatibility with current microfluidic setups. Full article

(This article belongs to the Special Issue Current Trends in Microfabrication Techniques for Lab-on-a-Chip and Biomedical Microdevices, 2nd Edition)

► Show Figures

Figure 1

32 pages, 17993 KB

Open AccessFeature PaperEditor’s ChoiceReview

Design, Fabrication, and Application of Large-Area Flexible Pressure and Strain Sensor Arrays: A Review

by Xikuan Zhang, Jin Chai, Yongfu Zhan, Danfeng Cui, Xin Wang and Libo Gao

Micromachines 2025, 16(3), 330; https://doi.org/10.3390/mi16030330 - 12 Mar 2025

Cited by 3 | Viewed by 2740

Abstract

The rapid development of flexible sensor technology has made flexible sensor arrays a key research area in various applications due to their exceptional flexibility, wearability, and large-area-sensing capabilities. These arrays can precisely monitor physical parameters like pressure and strain in complex environments, making [...] Read more.

The rapid development of flexible sensor technology has made flexible sensor arrays a key research area in various applications due to their exceptional flexibility, wearability, and large-area-sensing capabilities. These arrays can precisely monitor physical parameters like pressure and strain in complex environments, making them highly beneficial for sectors such as smart wearables, robotic tactile sensing, health monitoring, and flexible electronics. This paper reviews the fabrication processes, operational principles, and common materials used in flexible sensors, explores the application of different materials, and outlines two conventional preparation methods. It also presents real-world examples of large-area pressure and strain sensor arrays. Fabrication techniques include 3D printing, screen printing, laser etching, magnetron sputtering, and molding, each influencing sensor performance in different ways. Flexible sensors typically operate based on resistive and capacitive mechanisms, with their structural designs (e.g., sandwich and fork-finger) affecting integration, recovery, and processing complexity. The careful selection of materials—especially substrates, electrodes, and sensing materials—is crucial for sensor efficacy. Despite significant progress in design and application, challenges remain, particularly in mass production, wireless integration, real-time data processing, and long-term stability. To improve mass production feasibility, optimizing fabrication processes, reducing material costs, and incorporating automated production lines are essential for scalability and defect reduction. For wireless integration, enhancing energy efficiency through low-power communication protocols and addressing signal interference and stability are critical for seamless operation. Real-time data processing requires innovative solutions such as edge computing and machine learning algorithms, ensuring low-latency, high-accuracy data interpretation while preserving the flexibility of sensor arrays. Finally, ensuring long-term stability and environmental adaptability demands new materials and protective coatings to withstand harsh conditions. Ongoing research and development are crucial to overcoming these challenges, ensuring that flexible sensor arrays meet the needs of diverse applications while remaining cost-effective and reliable. Full article

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

► Show Figures

Figure 1

20 pages, 7265 KB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Wafer-Level Packaging Technology for SAW and BAW Filters

by Xinyue Liu, Wenjiao Pei, Jin Zhao, Rongbin Xu, Yi Zhong and Daquan Yu

Micromachines 2025, 16(3), 320; https://doi.org/10.3390/mi16030320 - 11 Mar 2025

Cited by 2 | Viewed by 2540

Abstract

This paper presents a comprehensive review of advancements in wafer-level packaging (WLP) technology, with a particular focus on its application in surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters. As wireless communication systems continue to evolve, there is an increasing demand [...] Read more.

This paper presents a comprehensive review of advancements in wafer-level packaging (WLP) technology, with a particular focus on its application in surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters. As wireless communication systems continue to evolve, there is an increasing demand for higher performance and miniaturization, which has made acoustic wave devices—especially SAW and BAW filters—crucial components in the Radio Frequency (RF) front-end systems of mobile devices. This review explores key developments in WLP technology, emphasizing novel materials, innovative structures, and advanced modeling techniques that have enabled the miniaturization and enhanced functionality of these filters. Additionally, the paper discusses the role of WLP in addressing challenges related to size reduction and integration, facilitating the creation of multi-functional devices with low manufacturing costs and high precision. Finally, it highlights the opportunities and future directions of WLP technology in the context of next-generation wireless communication standards. Full article

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

► Show Figures

Figure 1

11 pages, 2813 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Development of an Easy-to-Fabricate Microdevice for Three-Dimensional Culture and Its Application to Glomerular Endothelial Cell Culture

by Miyu Yamazaki, Yasuko Kobayashi and Kiichi Sato

Micromachines 2025, 16(3), 324; https://doi.org/10.3390/mi16030324 - 11 Mar 2025

Viewed by 690

Abstract

The development of an organ-on-a-chip to reproduce organ functions requires the incorporation of a vascular network within the tissue to transport the necessary nutrients. Tissues thicker than 200 µm cannot survive without a capillary network, necessitating the construction of a vascular network exceeding [...] Read more.

The development of an organ-on-a-chip to reproduce organ functions requires the incorporation of a vascular network within the tissue to transport the necessary nutrients. Tissues thicker than 200 µm cannot survive without a capillary network, necessitating the construction of a vascular network exceeding that thickness. Therefore, we focused on the development of an inexpensive and easy-to-fabricate device for thick three-dimensional(3D)-cultured tissues. This device does not have a conventional pillar array structure, and the nutrient supply to the cells from adjacent media channels is not obstructed. Additionally, this device does not require expensive soft lithography equipment or a high-precision 3D printer to fabricate the mold. Human glomerular endothelial cells and human dermal fibroblasts were co-cultured using this device, and a 3D network of vascular endothelial cells (200 µm thick) was successfully constructed. The results of this study are expected to contribute not only to the study of angiogenesis, but also to the development of 3D tissue models that require the incorporation of capillary networks as well as the development of vascularized organ-on-a-chip and disease models for drug screening. Full article

(This article belongs to the Section B2: Biofabrication and Tissue Engineering)

► Show Figures

Figure 1

20 pages, 18781 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Demonstration of Pattern Size Effects on Hydrophobic Nanocellulose Coatings with Regular Micron-Sized Island-like Geometrical Domains Created by Femtosecond Laser Micromachining

by Pieter Samyn, Patrick Cosemans and Olivier Malek

Micromachines 2025, 16(3), 289; https://doi.org/10.3390/mi16030289 - 28 Feb 2025

Viewed by 791

Abstract

As inspired by nature, wettability of bio-based material surfaces can be controlled by combining appropriate surface chemistries and topographies mimicking the structure of plant leaves or animals. The need for bio-based nanocellulose coatings with enhanced hydrophobic properties becomes technically relevant for extending their [...] Read more.

As inspired by nature, wettability of bio-based material surfaces can be controlled by combining appropriate surface chemistries and topographies mimicking the structure of plant leaves or animals. The need for bio-based nanocellulose coatings with enhanced hydrophobic properties becomes technically relevant for extending their applications in the technological domain with better protection and lifetime of the coatings. In this work, the water repellence of spray-coated nanocellulose coatings with hydrophobically modified cellulose microfiber (mCMF coatings), or hydrophobically modified cellulose nanofiber (mCNF coatings) was enhanced after femtosecond laser patterning. In particular, the influences of different island-like pattern geometries and pattern sizes were systematically studied. The island-like patterns were experimentally created with single posts that have variable sizes of the valleys (B = 30 to 15 µm) and top surface area (T = 120 to 15 µm), resulting in good resolution of the patterns down to the size of the laser beam diameter (15 µm). Depending on the intrinsic homogeneity and porosity of sprayed mCMF and mCNF coatings, the quality and resolution of the island-like patterns is better for the mCNF coatings with thinner and more homogeneous sizes of the cellulose nanofibrils. The increase in apparent water contact angle on patterned nanocellulose coatings can be estimated from the theoretical Cassie–Baxter state of wetting and shows maximum values up to θ_s = 128° (mCMF coatings), or θ_s = 140° (mCNF coatings), for the smallest pattern sizes in parallel with minimum contact angle hysteresis of Δθ = 14° (mCMF coatings), or Δθ < 9° (mCNF coatings). The study demonstrated that femtosecond laser patterning technology provides high flexibility and adaptivity to create surface patterns in appropriate dimensions with enhanced hydrophobicity of nanocellulose coatings. Full article

(This article belongs to the Special Issue Laser Micro/Nano-Fabrication)

► Show Figures

Figure 1

55 pages, 13764 KB

Open AccessFeature PaperEditor’s ChoiceReview

Progress in Polycrystalline SiC Growth by Low Pressure Chemical Vapor Deposition and Material Characterization

by Michail Gavalas, Yann Gallou, Didier Chaussende, Elisabeth Blanquet, Frédéric Mercier and Konstantinos Zekentes

Micromachines 2025, 16(3), 276; https://doi.org/10.3390/mi16030276 - 27 Feb 2025

Viewed by 2191

Abstract

The purpose of this paper is to give a review on the state of the art of polycrystalline SiC material grown by low-pressure chemical vapor deposition (LPCVD). Nowadays, LPCVD is the main technique used for the deposition of polycrystalline SiC, both in academic [...] Read more.

The purpose of this paper is to give a review on the state of the art of polycrystalline SiC material grown by low-pressure chemical vapor deposition (LPCVD). Nowadays, LPCVD is the main technique used for the deposition of polycrystalline SiC, both in academic research and industry. Indeed, the LPCVD technique is today the most mature technique to grow high purity polycrystalline thin films with controlled thickness and structure over a large area (>50 cm) and/or 3D substrate. Its ability to have a high degree of modification on the growth conditions and the chosen precursor system allows the deposition of polycrystalline SiC films in various substrates with tailored properties according to the desired application. After a short introduction on the SiC material and its growth by the LPCVD technique, a review of theoretical studies (thermodynamics and kinetics) related to the CVD SiC growth process is given. A synthesis of the experimental studies is made focusing on the effect of the growth conditions on the properties of the deposited SiC polycrystalline material. Despite the numerous results, a full understanding of them is limited due to the complexity of the LPCVD process and the polycrystalline SiC structure. The conclusions show that the growth conditions, like temperature, chamber pressure, (C/Si)_(g), (Cl/Si)_(g), and doping have an impact on the microstructure and on the corresponding properties of the polycrystalline SiC films. Future perspectives are given in order to improve our understanding on the polycrystalline–SiC–LPCVD process and to enable the growth of tailor-made polycrystalline SiC films for future applications. Full article

(This article belongs to the Special Issue Research Progress of Advanced SiC Semiconductors)

► Show Figures

Figure 1

17 pages, 3028 KB

Open AccessFeature PaperEditor’s ChoiceReview

Advances in Triboelectric Nanogenerators for Microbial Disinfection

by Jinyoung Jeon, Donghyeon Kang and Sang-Woo Kim

Micromachines 2025, 16(3), 281; https://doi.org/10.3390/mi16030281 - 27 Feb 2025

Cited by 1 | Viewed by 1277

Abstract

The global COVID-19 pandemic has highlighted the pivotal role of microbial disinfection technologies, driving the demand for innovative, efficient, and sustainable solutions. Triboelectric technology, known for efficiently converting ambient mechanical energy into electrical energy, has emerged as a promising candidate to address these [...] Read more.

The global COVID-19 pandemic has highlighted the pivotal role of microbial disinfection technologies, driving the demand for innovative, efficient, and sustainable solutions. Triboelectric technology, known for efficiently converting ambient mechanical energy into electrical energy, has emerged as a promising candidate to address these needs. Self-powered electro-based microbial disinfection using triboelectric nanogenerators (TENGs) has emerged as a promising solution. TENGs have demonstrated effective disinfection capabilities in various settings, including water, air, surfaces, and wounds. This review explores the advancements in TENG-based microbial disinfection, highlighting its mechanisms and applications. By utilizing triboelectric technology, it provides comprehensive insights into the development of sustainable and efficient solutions for microbial control across diverse environments. Full article

(This article belongs to the Special Issue Triboelectric Nanogenerators: From Fundamental Research to Applications)

► Show Figures

Figure 1

15 pages, 11779 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrospun Polycaprolactone (PCL) Nanofibers Induce Elongation and Alignment of Co-Cultured Primary Cortical Astrocytes and Neurons

by Kayleigh Nutt, Zoe Dombros-Ryan, Ruxandra Birea, Emily Victoria Franks, Sarah Eastham, Morgan Godwin, Chris F. Adams, Divya Maitreyi Chari and Stuart Iain Jenkins

Micromachines 2025, 16(3), 256; https://doi.org/10.3390/mi16030256 - 25 Feb 2025

Cited by 1 | Viewed by 1545

Abstract

Neuromimetic in vitro models, simulating in vivo architecture/organization, are urgently needed to reduce experimental reliance on live animals. Our group recently reported a novel brain tissue derivation protocol, simultaneously deriving all major cortical cell types (including immune cells) in a facile protocol, generating [...] Read more.

Neuromimetic in vitro models, simulating in vivo architecture/organization, are urgently needed to reduce experimental reliance on live animals. Our group recently reported a novel brain tissue derivation protocol, simultaneously deriving all major cortical cell types (including immune cells) in a facile protocol, generating a network of neurons in a single growth medium, which was interfaced with nanomaterials. This represents a significant advance, as tissue engineers overwhelmingly use diverse methods to derive and combine individual brain cells for materials-interfacing. However, this multicellular model lacked cellular directionality/structural organization (unlike the highly organized cortical circuits in vivo). Synthetic nanofiber constructs are of high value in tissue engineering, providing directional cues for cells. Most neuro-nanofiber studies employ simple monocultures of astrocytes/neurons and commonly use peripheral neurons rather than central nervous system populations. Here, we have interfaced our complex brain model (neurons/astrocytes derived simultaneously) with randomly oriented or aligned polycaprolactone (PCL) fiber meshes. Both cell types showed targeted extension along aligned fibers versus coverslips or random fibers. A new analysis method developed in-house demonstrated that peak orientations for astrocytes and neurons correlated with aligned nanofibers. Our data support the concept that nanofiber scaffolds can achieve organized growth of mixed cortical neural cell populations, mimicking neural architecture. Full article

(This article belongs to the Special Issue The 15th Anniversary of Micromachines)

► Show Figures

Figure 1

18 pages, 13167 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Research on Low-Profile Directional Flexible Antenna with 3D Coplanar Waveguide for Partial Discharge Detection

by Yan Mi, Wentao Liu, Yiqin Peng, Lei Deng, Benxiang Shu, Xiaopeng Wang and Songyuan Li

Micromachines 2025, 16(3), 253; https://doi.org/10.3390/mi16030253 - 24 Feb 2025

Viewed by 1554

Abstract

Due to the challenges in antenna installation and detection performance caused by metal obstruction along the propagation path at a Gas-Insulated Switchgear (GIS) cable terminal, as well as the adverse effects of environmental interference on the detection of partial discharge (PD) by existing [...] Read more.

Due to the challenges in antenna installation and detection performance caused by metal obstruction along the propagation path at a Gas-Insulated Switchgear (GIS) cable terminal, as well as the adverse effects of environmental interference on the detection of partial discharge (PD) by existing flexible antennas, this paper proposes a directional flexible antenna design to mitigate these issues and improve detection performance. The proposed design employs a coplanar waveguide (CPW)-fed monopole antenna structure, where the grounding plane is extended to the back of the antenna to enhance directional reception. The designed flexible antenna measures 88.5 × 70 × 20 mm, and its low-profile design allows it to be easily mounted on the outer wall of the epoxy sleeve at the GIS cable terminal. The measurement results show that the flexible antenna has a Voltage Standing Wave Ratio (VSWR) of less than 2 in the 0.541–3 GHz frequency range. It also maintains stable impedance characteristics across various bending radii, with an average effective height of 10.79 mm in the 0.3–1.5 GHz frequency range. A GIS cable terminal PD experimental platform was established, and the experimental results demonstrate that the bending has minimal impact on the detection performance of the flexible antenna, which can cover the detection range of the GIS cable terminal; metal obstruction significantly impacts the PD signal amplitude, and the designed flexible antenna is suitable for detecting PDs in confined spaces with metal obstruction. Full article

(This article belongs to the Section E：Engineering and Technology)

► Show Figures

Figure 1

20 pages, 7741 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Mode-Localized Micro-Electromechanical System Accelerometer with Force Rebalance Closed-Loop Control

by Bowen Wang, Zhenxiang Qi, Kunfeng Wang, Zhaoyang Zhai, Zheng Wang and Xudong Zou

Micromachines 2025, 16(3), 248; https://doi.org/10.3390/mi16030248 - 21 Feb 2025

Cited by 1 | Viewed by 2391

Abstract

This article proposes a force rebalance control scheme based on a mode-localized resonant accelerometer (ML-RXL), which is applied to address the limited measurement range problem of the ML-RXL. For the first time, an empirical response model of the weakly coupling resonators for the [...] Read more.

This article proposes a force rebalance control scheme based on a mode-localized resonant accelerometer (ML-RXL), which is applied to address the limited measurement range problem of the ML-RXL. For the first time, an empirical response model of the weakly coupling resonators for the amplitude ratio output is established. Based on this, this paper builds an overall model of the force rebalance control system to analyze the sensitivity characteristics by simulations, which demonstrates that the scheme can effectively broaden the linear measurement range. It is demonstrated that the sensor exhibits a highly linear output within a measurement range of ±1 g, with a sensitivity of the feedback-control voltage output measured at 2.94 V/g. The measurement range is expanded by at least 6.7 times. Moreover, the results show that the minimum input-referred acceleration noise density of the sensor for the force rebalance control scheme is 3.29 μg/rtHz, and that the best bias instability is optimized to 5.34 μg with an integral time of 0.64 s. Full article

► Show Figures

Figure 1

26 pages, 3046 KB

Open AccessFeature PaperEditor’s ChoiceReview

Polymerase Chain Reaction Chips for Biomarker Discovery and Validation in Drug Development

by Dang-Khoa Vo and Kieu The Loan Trinh

Micromachines 2025, 16(3), 243; https://doi.org/10.3390/mi16030243 - 20 Feb 2025

Viewed by 2285

Abstract

Polymerase chain reaction (PCR) chips are advanced, microfluidic platforms that have revolutionized biomarker discovery and validation because of their high sensitivity, specificity, and throughput levels. These chips miniaturize traditional PCR processes for the speed and precision of nucleic acid biomarker detection relevant to [...] Read more.

Polymerase chain reaction (PCR) chips are advanced, microfluidic platforms that have revolutionized biomarker discovery and validation because of their high sensitivity, specificity, and throughput levels. These chips miniaturize traditional PCR processes for the speed and precision of nucleic acid biomarker detection relevant to advancing drug development. Biomarkers, which are useful in helping to explain disease mechanisms, patient stratification, and therapeutic monitoring, are hard to identify and validate due to the complexity of biological systems and the limitations of traditional techniques. The challenges to which PCR chips respond include high-throughput capabilities coupled with real-time quantitative analysis, enabling researchers to identify novel biomarkers with greater accuracy and reproducibility. More recent design improvements of PCR chips have further expanded their functionality to also include digital and multiplex PCR technologies. Digital PCR chips are ideal for quantifying rare biomarkers, which is essential in oncology and infectious disease research. In contrast, multiplex PCR chips enable simultaneous analysis of multiple targets, therefore simplifying biomarker validation. Furthermore, single-cell PCR chips have made it possible to detect biomarkers at unprecedented resolution, hence revealing heterogeneity within cell populations. PCR chips are transforming drug development, enabling target identification, patient stratification, and therapeutic efficacy assessment. They play a major role in the development of companion diagnostics and, therefore, pave the way for personalized medicine, ensuring that the right patient receives the right treatment. While this tremendously promising technology has exhibited many challenges regarding its scalability, integration with other omics technologies, and conformity with regulatory requirements, many still prevail. Future breakthroughs in chip manufacturing, the integration of artificial intelligence, and multi-omics applications will further expand PCR chip capabilities. PCR chips will not only be important for the acceleration of drug discovery and development but also in raising the bar in improving patient outcomes and, hence, global health care as these technologies continue to mature. Full article

(This article belongs to the Special Issue PCR Chips for Biomarker Discovery and Validation in Drug Development)

► Show Figures

Figure 1

20 pages, 5569 KB

Open AccessFeature PaperEditor’s ChoiceReview

Design and Fabrication of Microelectrodes for Dielectrophoresis and Electroosmosis in Microsystems for Bio-Applications

by Mengren Wu, Zijian Liu and Yuan Gao

Micromachines 2025, 16(2), 190; https://doi.org/10.3390/mi16020190 - 7 Feb 2025

Cited by 1 | Viewed by 4681

Abstract

Microfluidic technology has emerged as a multidisciplinary field, integrating fluid dynamics, electronics, materials science, etc., enabling precise manipulation of small volumes of fluids and particles for various bio-applications. Among the forms of energy integrated into microfluidic systems, electric fields are particularly advantageous for [...] Read more.

Microfluidic technology has emerged as a multidisciplinary field, integrating fluid dynamics, electronics, materials science, etc., enabling precise manipulation of small volumes of fluids and particles for various bio-applications. Among the forms of energy integrated into microfluidic systems, electric fields are particularly advantageous for achieving precise control at the microscale. This review focuses on the design and fabrication of microelectrodes that drive electrokinetic phenomena, dielectrophoresis (DEP) and electroosmotic flow (EOF), key techniques for particle and fluid manipulation in microfluidic devices. DEP relies on non-uniform electric fields to manipulate particles based on their dielectric properties, while EOF utilizes uniform electric fields to generate consistent fluid flow across microchannels. Advances in microelectrode fabrication, including photolithography, soft lithography, and emerging non-cleanroom techniques, are discussed. Additionally, the review explores innovative approaches such as rapid prototyping, contactless electrodes, and three-dimensional structures, along with material considerations like conductive polymers and carbon composites. The review discusses the role of microelectrodes in enhancing device functionality, scalability, and reliability. The paper also identifies challenges, including the need for improved fabrication reproducibility and multifunctional integration. Finally, potential future research directions are proposed to further optimize DEP- and EOF-based microsystems for advanced biomedical and diagnostic applications. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI