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Micromachines

Micromachines is a peer-reviewed, open access journal on the science and technology of small structures, devices and systems, published monthly online by MDPI. The Chinese Society of Micro-Nano Technology (CSMNT) is affiliated with Micromachines and its members receive discounts on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, PMC, Ei Compendex, dblp, and other databases.
Journal Rank: JCR - Q2 (Physics, Applied) / CiteScore - Q2 (Mechanical Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.2 days after submission; acceptance to publication is undertaken in 1.8 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Micromachines.
Companion journal: Micro.

Impact Factor: 3.0 (2023); 5-Year Impact Factor: 3.0 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2072-666X

Latest Articles

12 pages, 1235 KiB

Open AccessArticle

Modeling the Reaction Process for the Synthesis of Ethyl Chrysanthemate from Ethyl Diazoacetate in a Micro-Flow Platform

by Dawei Xin and Yangcheng Lu

Micromachines 2025, 16(2), 125; https://doi.org/10.3390/mi16020125 - 22 Jan 2025

Ethyl diazoacetate can react with 2,5-dimethyl-2,4-hexadiene to yield ethyl chrysanthemumate, an important raw material for synthesizing various pesticides. In conventional conditions, this cyclopropanation process suffers from low efficiency and yield due to ethyl diazoacetate. This demands more understanding of the catalytic process from [...] Read more.

Ethyl diazoacetate can react with 2,5-dimethyl-2,4-hexadiene to yield ethyl chrysanthemumate, an important raw material for synthesizing various pesticides. In conventional conditions, this cyclopropanation process suffers from low efficiency and yield due to ethyl diazoacetate. This demands more understanding of the catalytic process from the mechanism and modeling to find a solution. In this work, we set up a micro-flow platform to carefully study the kinetic characteristics of the cyclopropanation reaction of ethyl diazoacetate catalyzed by a complex of copper stearate and phenylhydrazine. Through a reasonable simplification of the reaction network, we established a reaction kinetic model with good prediction capacity within a wide range of operating conditions. It provides a basis for guiding the development of efficient conversion processes and condition optimization. Full article

(This article belongs to the Section C：Chemistry)

13 pages, 1568 KiB

Open AccessArticle

Development of a Tool for Verifying Leakage Detection in Microfluidic Systems

by Ali Bozorgnezhad, Luke Herbertson and Suvajyoti Guha

Micromachines 2025, 16(2), 124; https://doi.org/10.3390/mi16020124 - 22 Jan 2025

While submissions of microfluidic-based medical devices to the Food and Drug Administration (FDA) have increased in recent years, leakage remains a common but difficult failure mode to detect in microfluidic systems. Here, we have developed a sensitive tool to measure and verify leakages [...] Read more.

While submissions of microfluidic-based medical devices to the Food and Drug Administration (FDA) have increased in recent years, leakage remains a common but difficult failure mode to detect in microfluidic systems. Here, we have developed a sensitive tool to measure and verify leakages ranging from 0.1% to 10% in leakage detection systems, which can then be used to detect leak in microfluidic devices. Our methodology includes an analytical model that applies hydrodynamic resistance using different fluid-contacting elements (e.g., tubing, junctions, and connectors) to tune the leakage rate based on the application-specific acceptance criteria. We then used three polymer-based microfluidic systems to target leakage rates of approximately 0.1, 1.0, and 10%. The experimental uncertainties in Polyether Ether Ketone (PEEK) tubing were 23.08%, 13.64%, and 1.16%, respectively, while the PEEK-Coated Fused Silica (PEEKsil) tubing system had errors of 0.00%, 0.72%, and 1.59%, respectively, relative to the theoretical values for the same target leak rates. The commonly used commercial grade Cyclic Olefin Copolymer (COC) microfluidic chips produced errors of 7.69% and 5.05%, respectively, for target leakage rates of 0.24% and 1.88%. We anticipate that the proposed bench test method can be useful for device developers as a verification tool for leakage detection systems before assessing flow-mediated leakage failure modes in microfluidic medical devices. Full article

(This article belongs to the Section B4: Point-of-Care Devices)

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15 pages, 4621 KiB

Open AccessArticle

MXene–MWCNT Conductive Network for Long-Lasting Wearable Strain Sensors with Gesture Recognition Capabilities

by Fei Wang, Hongchen Yu, Xue Lv, Xingyu Ma, Quanlin Qu, Hanning Wang, Da Chen and Yijian Liu

Micromachines 2025, 16(2), 123; https://doi.org/10.3390/mi16020123 - 22 Jan 2025

In this work, a conductive composite film composed of multi-walled carbon nanotubes (MWCNTs) and multi-layer Ti₃C₂Tx MXene nanosheets is used to construct a strain sensor on sandpaper Ecoflex substrate. The composite material forms a sophisticated conductive network with exceptional [...] Read more.

In this work, a conductive composite film composed of multi-walled carbon nanotubes (MWCNTs) and multi-layer Ti₃C₂Tx MXene nanosheets is used to construct a strain sensor on sandpaper Ecoflex substrate. The composite material forms a sophisticated conductive network with exceptional electrical conductivity, resulting in sensors with broad detection ranges and high sensitivities. The findings indicate that the strain sensing range of the Ecoflex/Ti₃C₂Tx/MWCNT strain sensor, when the mass ratio is set to 5:2, extends to 240%, with a gauge factor (GF) of 933 within the strain interval from 180% to 240%. The strain sensor has demonstrated its robustness by enduring more than 33,000 prolonged stretch-and-release cycles at 20% cyclic tensile strain. Moreover, a fast response time of 200 ms and detection limit of 0.05% are achieved. During application, the sensor effectively enables the detection of diverse physiological signals in the human body. More importantly, its application in a data glove that is coupled with machine learning and uses the Support Vector Machine (SVM) model trained on the collected gesture data results in an impressive recognition accuracy of 93.6%. Full article

(This article belongs to the Special Issue New Advances in Wearable and Flexible Sensor Devices and Their Future Prospects)

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22 pages, 2271 KiB

Open AccessArticle

Design Parameters Affecting the Performance of Vortex-Induced Vibration Harvesters

by Alberto Pasetto, Michele Tonan, Federico Moro and Alberto Doria

Micromachines 2025, 16(2), 122; https://doi.org/10.3390/mi16020122 - 22 Jan 2025

Vortex-induced vibration harvesters are usually equipped with small piezoelectric patches mounted near the cantilever clamp, where the largest longitudinal stress occurs. This paper, aiming to improve energy harvesting performance, investigates the possibilities of extending the patch length and modifying the length and mass [...] Read more.

Vortex-induced vibration harvesters are usually equipped with small piezoelectric patches mounted near the cantilever clamp, where the largest longitudinal stress occurs. This paper, aiming to improve energy harvesting performance, investigates the possibilities of extending the patch length and modifying the length and mass of a bluff body mounted on a harvester to induce vortex shedding. A novel analytical model based on dimensionless numbers is presented to determine the output voltage generated by a cantilever harvester subjected to periodic vortex shedding. This model highlights the design parameters having the largest influence on harvester performance and provides guidance to the planning of experimental tests and the interpretation of experimental results. Some prototype harvesters with different designs are built. First, experimental tests are carried out to identify the natural frequencies and damping ratios of the prototypes; then, the prototypes are tested in a wind tunnel to assess energy harvesting performance. The best performance is achieved when the patch length is about 20% of the cantilever length, the bluff body is long, and its mass reaches the minimum value. This result agrees with the prediction of the model. Full article

(This article belongs to the Special Issue Piezoelectric MEMS/NEMS—Materials, Devices, and Applications, Third Edition)

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14 pages, 5008 KiB

Open AccessArticle

The Effect of BEOL Design Factors on the Thermal Reliability of Flip-Chip Chip-Scale Packaging

by Dejian Li, Bofu Li, Shunfeng Han, Dameng Li, Baobin Yang, Baoliang Gong, Zhangzhang Zhang, Chang Yu and Pei Chen

Micromachines 2025, 16(2), 121; https://doi.org/10.3390/mi16020121 - 22 Jan 2025

With the development of high-density integrated chips, low-k dielectric materials are used in the back end of line (BEOL) to reduce signal delay. However, due to the application of fine-pitch packages with high-hardness copper pillars, BEOL is susceptible to chip package interaction (CPI), [...] Read more.

With the development of high-density integrated chips, low-k dielectric materials are used in the back end of line (BEOL) to reduce signal delay. However, due to the application of fine-pitch packages with high-hardness copper pillars, BEOL is susceptible to chip package interaction (CPI), which leads to reliability issues such as the delamination of interlayer dielectric (ILD) layers. In order to improve package reliability, the effect of CPI at multi-scale needs to be explored in terms of package integration. In this paper, the stress of BEOL in the flip-chip chip-scale packaging (FCCSP) model during thermal cycling is investigated by using the finite-element-based sub-model approach. A three-dimensional (3D) multi-level finite element model is established based on the FCCSP. The wiring layers were treated by the equivalent homogenization method to ensure high prediction accuracy. The stress distribution of the BEOL around the critical bump was analyzed. The cracking risk of the interface layer of the BEOL was assessed by pre-cracking at a dangerous location. In addition, the effects of the epoxy molding compound (EMC) thickness, polyimide (PI) opening, and coefficient of thermal expansion (CTE) of the underfill on cracking were investigated. The simulation results show that the first principal stress of BEOL is higher at high-temperature moments than at low-temperature moments, and mainly concentrated near the PI opening. Compared with the oxide layer, the low-k layer has a higher risk of cracking. A smaller EMC thickness, lower CTE of the underfill, and larger PI opening help to reduce the risk of cracking in the BEOL. Full article

(This article belongs to the Special Issue 3D Integration: Trends, Challenges and Opportunities)

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17 pages, 3843 KiB

Open AccessArticle

Metal Oxide Nanocatalysts for the Electrochemical Detection of Propofol

by David C. Ferrier, Janice Kiely and Richard Luxton

Micromachines 2025, 16(2), 120; https://doi.org/10.3390/mi16020120 - 22 Jan 2025

Propofol is one of the most widely used intravenous drugs for anaesthesia and sedation and is one of the most commonly used drugs in intensive care units for the sedation of mechanically ventilated patients. The correct dosage of propofol is of high importance, [...] Read more.

Propofol is one of the most widely used intravenous drugs for anaesthesia and sedation and is one of the most commonly used drugs in intensive care units for the sedation of mechanically ventilated patients. The correct dosage of propofol is of high importance, but there is currently a lack of suitable point-of-care techniques for determining blood propofol concentrations. Here, we present a cytochrome P450 2B6/carbon nanotube/graphene oxide/metal oxide nanocomposite sensor for discrete measurement of propofol concentration. Propofol is converted into a quinol/quinone redox couple by the enzyme and the nanocomposite enables sensitive and rapid detection. The metal oxide nanoparticles are synthesised via green synthesis and a variety of metal oxides and mixed metal oxides are investigated to determine the optimal nanocatalyst. Converting propofol into the redox couple allows for the measurement to take place over different potential ranges, enabling interference from common sources such as paracetamol and uric acid to be avoided. It was found that nanocomposites containing copper titanium oxide nanoparticles offered the best overall performance and electrodes functionalised with such nanocomposites demonstrated a limit of detection in bovine serum of 0.5 µg/mL and demonstrated a linear response over the therapeutic range of propofol with a sensitivity of 4.58 nA/μg/mL/mm². Full article

(This article belongs to the Special Issue Metal Nanoparticles: Preparing and Advanced Applications)

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12 pages, 3102 KiB

Open AccessArticle

Investigation of Modal Characteristics of Silicon Nitride Ridge Waveguides for Enhanced Refractive Index Sensing

by Muhammad A. Butt, Lukasz Kozlowski, Mateusz Słowikowski, Marcin Juchniewicz, Dagmara Drecka, Maciej Filipiak, Michał Golas, Bartłomiej Stonio, Michal Dudek and Ryszard Piramidowicz

Micromachines 2025, 16(2), 119; https://doi.org/10.3390/mi16020119 - 21 Jan 2025

This paper investigates the wavelength-dependent sensitivity of a ridge waveguide based on a silicon nitride (Si₃N₄) platform, combining numerical analysis and experimental validation. In the first part, the modal characteristics of a Si₃N₄ ridge waveguide are [...] Read more.

This paper investigates the wavelength-dependent sensitivity of a ridge waveguide based on a silicon nitride (Si₃N₄) platform, combining numerical analysis and experimental validation. In the first part, the modal characteristics of a Si₃N₄ ridge waveguide are analyzed in detail, focusing on the effective refractive index (n_eff), evanescent field ratio (EFR), and propagation losses (α_prop). These parameters are critical for understanding the interplay of guided light with the surrounding medium and optimizing waveguide design for sensing applications. In the second part, the wavelength-dependent sensitivity of a racetrack ring resonator (RTRR) based on the Si₃N₄ waveguide is experimentally demonstrated. The results demonstrate a clear increase in the sensitivity of the RTRR, rising from 116.3 nm/RIU to 143.3 nm/RIU as the wavelength shifts from 1520 nm to 1600 nm. This trend provides valuable insights into the device’s enhanced performance at longer wavelengths, underscoring its potential for applications requiring high sensitivity in this spectral range. Full article

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

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22 pages, 5992 KiB

Open AccessReview

IGZO-Based Electronic Device Application: Advancements in Gas Sensor, Logic Circuit, Biosensor, Neuromorphic Device, and Photodetector Technologies

by Youngmin Han, Juhyung Seo, Dong Hyun Lee and Hocheon Yoo

Micromachines 2025, 16(2), 118; https://doi.org/10.3390/mi16020118 - 21 Jan 2025

Metal oxide semiconductors, such as indium gallium zinc oxide (IGZO), have attracted significant attention from researchers in the fields of liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) for decades. This interest is driven by their high electron mobility of over ~10 [...] Read more.

Metal oxide semiconductors, such as indium gallium zinc oxide (IGZO), have attracted significant attention from researchers in the fields of liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) for decades. This interest is driven by their high electron mobility of over ~10 cm²/V·s and excellent transmittance of more than ~80%. Amorphous IGZO (a-IGZO) offers additional advantages, including compatibility with various processes and flexibility making it suitable for applications in flexible and wearable devices. Furthermore, IGZO-based thin-film transistors (TFTs) exhibit high uniformity and high-speed switching behavior, resulting in low power consumption due to their low leakage current. These advantages position IGZO not only as a key material in display technologies but also as a candidate for various next-generation electronic devices. This review paper provides a comprehensive overview of IGZO-based electronics, including applications in gas sensors, biosensors, and photosensors. Additionally, it emphasizes the potential of IGZO for implementing logic gates. Finally, the paper discusses IGZO-based neuromorphic devices and their promise in overcoming the limitations of the conventional von Neumann computing architecture. Full article

(This article belongs to the Special Issue Semiconductor and Energy Materials and Processing Technology)

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9 pages, 216 KiB

Open AccessEditorial

Editorial for the Glassy Materials and Micro/Nano Devices Section

by Giancarlo C. Righini

Micromachines 2025, 16(2), 117; https://doi.org/10.3390/mi16020117 - 21 Jan 2025

Glass is an amorphous solid, renowned for its transparency and versatility, and has been widely used for centuries in both scientific instruments and daily life [...] Full article

(This article belongs to the Section D4: Glassy Materials and Micro/Nano Devices)

10 pages, 8031 KiB

Open AccessArticle

An All-in-One Testing Chip for the Simultaneous Measurement of Multiple Thermoelectric Parameters in Doped Polysilicon

by Lei Shi, Na Zhou, Jintao Wu, Meng Shi, Yizhi Shi, Cheng Lei and Haiyang Mao

Micromachines 2025, 16(2), 116; https://doi.org/10.3390/mi16020116 - 21 Jan 2025

Polysilicon is widely used as a thermoelectric material due to its CMOS compatibility and tunability through doping. The accurate measurement of the thermoelectric parameters—such as the Seebeck coefficient, thermal conductivity, and electrical resistivity—of polysilicon with various doping conditions is essential for designing and [...] Read more.

Polysilicon is widely used as a thermoelectric material due to its CMOS compatibility and tunability through doping. The accurate measurement of the thermoelectric parameters—such as the Seebeck coefficient, thermal conductivity, and electrical resistivity—of polysilicon with various doping conditions is essential for designing and fabricating high-performance thermopile sensors. This work presents an all-in-one testing chip that incorporates double-layer thermoelectric structures on a suspended membrane-based supporting layer, with polysilicon constituting at least one of these thermoelectric layers. By employing a differential calculation approach in conjunction with thermal imaging methods, we could simultaneously measure various thermoelectric parameters—including resistivity, the Seebeck coefficient, and thermal conductivity—of polysilicon under different doping conditions. Furthermore, the method proposed in this study provides a means for accurately obtaining thermoelectric parameters for other materials, thereby facilitating the design and optimization of thermoelectric devices. Full article

(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications)

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24 pages, 6382 KiB

Open AccessArticle

Mechanistic Modelling of Coupled UV Energy Penetration and Resin Flow Dynamics in Digital Light Processing (DLP)-Based Microfluidic Chip Printing

by Xinhui Wang, Antony Seng Kai Kho, Jinghang Liu, Tianyu Mao, Michael D. Gilchrist and Nan Zhang

Micromachines 2025, 16(2), 115; https://doi.org/10.3390/mi16020115 - 21 Jan 2025

Digital light processing (DLP) technology has emerged as a promising approach for fabricating high-precision microfluidic chips due to its exceptional resolution and rapid prototyping capabilities. However, UV energy penetration and resin flow dynamics during layer-by-layer printing introduce significant challenges for microchannel printing, particularly [...] Read more.

Digital light processing (DLP) technology has emerged as a promising approach for fabricating high-precision microfluidic chips due to its exceptional resolution and rapid prototyping capabilities. However, UV energy penetration and resin flow dynamics during layer-by-layer printing introduce significant challenges for microchannel printing, particularly in controlling microchannel over-curing. In this study, a novel 3D DLP over-curing interaction model (DLP-OCIM) was developed to investigate the coupled effects of UV energy penetration and directional resin flow on the over-cured structure formation of microchannels. COMSOL Multiphysics 6.1 simulations incorporating UV light propagation, photopolymerization kinetics, and resin flow dynamics revealed that microchannel over-curing is a result of both energy infiltration through previously cured layers and periodic resin flow induced by the peeling process. Experimental validation using linear and annular microfluidic chips demonstrated that increasing layer thickness induces progressive over-curing, leading to inclined cross-sectional structures. Additionally, the microchannel geometry and size significantly influence resin flow patterns, with shorter transverse microchannels producing flatter over-cured profiles compared to their longitudinal counterparts. This study provides the first comprehensive analysis of the dynamic interplay between UV energy penetration and resin flow during DLP-based microchannel fabrication, offering valuable process insights and optimization strategies for enhancing shape fidelity and printing accuracy in high-resolution microfluidic chips. Full article

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

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19 pages, 2058 KiB

Open AccessArticle

A Compact Device Model for a Piezoelectric Nano-Transistor

by L. Neil McCartney, Louise E. Crocker, Louise Wright and Ivan Rungger

Micromachines 2025, 16(2), 114; https://doi.org/10.3390/mi16020114 - 21 Jan 2025

An approximate compact model was developed to provide a convenient method of exploring the initial design space when investigating the performance of micro-electronic devices such as nano-scaled piezoelectronic transistors, where fast ball-park estimates can be very helpful. First of all, the compact model [...] Read more.

An approximate compact model was developed to provide a convenient method of exploring the initial design space when investigating the performance of micro-electronic devices such as nano-scaled piezoelectronic transistors, where fast ball-park estimates can be very helpful. First of all, the compact model was verified by comparing its predictions with those of accurate axi-symmetric finite element analysis (FEA) using special boundary and interface conditions that enable the replication of the analytical model behaviour. Verification is achieved for a radio frequency (RF) switch and a smaller very-large-scale integrated (VLSI) device, where percentage differences between the compact and FEA model predictions are of the order 10⁻⁴ for the RF switch and 10⁻⁵ for the VLSI device. This confirms the consistency of complex property data (especially electro-thermo-elastic constants) and geometrical parameter input to both types of models and convincingly demonstrates that the analytical models and FEA for the two devices have been implemented correctly. A second type of boundary and interface condition is also used that is designed to replicate the actual behaviour of the devices in practice. The boundary and interface constraints applied for the verification procedure are relaxed so that there is perfect interface bonding between layers. For this unconstrained case, the resulting deformation is very complex, involving both bending effects and edge effects arising from property mismatches between neighbouring layers. The results for the RF switch show surprisingly good agreement between the predictions of the analytical and FEA results, provided the thickness of the piezoelectric layer is not too thick, implying that the analytical model should help to reduce the parameter design space for such devices. However, for the VLSI device, our results indicate that the compact model leads to much larger errors. For such systems, the compact model is unlikely to be able to reliably reduce the parameter design space, implying that accurate FEA will then need to be used. Full article

(This article belongs to the Special Issue Piezoelectric Devices and System in Micromachines)

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16 pages, 5458 KiB

Open AccessArticle

Enhanced Performance of Novel Amorphous Silicon Carbide Microelectrode Arrays in Rat Motor Cortex

by Pegah Haghighi, Eleanor N. Jeakle, Brandon S. Sturgill, Justin R. Abbott, Elysandra Solis, Veda S. Devata, Gayathri Vijayakumar, Ana G. Hernandez-Reynoso, Stuart F. Cogan and Joseph J. Pancrazio

Micromachines 2025, 16(2), 113; https://doi.org/10.3390/mi16020113 - 21 Jan 2025

Implantable microelectrode arrays (MEAs) enable the recording of electrical activity from cortical neurons for applications that include brain–machine interfaces. However, MEAs show reduced recording capabilities under chronic implantation conditions. This has largely been attributed to the brain’s foreign body response, which is marked [...] Read more.

Implantable microelectrode arrays (MEAs) enable the recording of electrical activity from cortical neurons for applications that include brain–machine interfaces. However, MEAs show reduced recording capabilities under chronic implantation conditions. This has largely been attributed to the brain’s foreign body response, which is marked by neuroinflammation and gliosis in the immediate vicinity of the MEA implantation site. This has prompted the development of novel MEAs with either coatings or architectures that aim to reduce the tissue response. The present study examines the comparative performance of multi-shank planar, silicon-based devices and low-flexural-rigidity amorphous silicon carbide (a-SiC) MEAs that have a similar architecture but differ with respect to the shank cross-sectional area. Data from a-SiC arrays were previously reported in a prior study from our group. In a manner consistent with the prior work, larger cross-sectional area silicon-based arrays were implanted in the motor cortex of female Sprague-Dawley rats and weekly recordings were made for 16 weeks after implantation. Single unit metrics from the recordings were compared over the implantation period between the device types. Overall, the expression of single units measured from a-SiC devices was significantly higher than for silicon-based MEAs throughout the implantation period. Immunohistochemical analysis demonstrated reduced neuroinflammation and gliosis around the a-SiC MEAs compared to silicon-based devices. Our findings demonstrate that the a-SiC MEAs with a smaller shank cross-sectional area can record single unit activity with more stability and exhibit a reduced inflammatory response compared to the silicon-based device employed in this study. Full article

(This article belongs to the Special Issue Flexible and Wearable Sensors, 3rd Edition)

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17 pages, 7273 KiB

Open AccessArticle

Measurement and Analysis of Interconnects’ Resonance and Signal/Power Integrity Degradation in Glass Packages

by Youngwoo Kim

Micromachines 2025, 16(1), 112; https://doi.org/10.3390/mi16010112 - 20 Jan 2025

In this article, resonance phenomena of high-speed interconnects and power delivery networks in glass packages are measured and analyzed. The resonances are generated in the interconnection by the physical dimension, cancelation of reactance components, and modes. When the resonances are generated in the [...] Read more.

In this article, resonance phenomena of high-speed interconnects and power delivery networks in glass packages are measured and analyzed. The resonances are generated in the interconnection by the physical dimension, cancelation of reactance components, and modes. When the resonances are generated in the operation frequency band, the signal/power integrity of the interconnect can be affected. As such, resonances generated in high-speed interconnects increase insertion loss, which degrades signal integrity. Also, resonances of the power delivery network (PDN) associated with boundary conditions increase PDN impedance, which degrades power integrity by generating power/ground noise and return current discontinuity of through vias. Recently, glass packaging has been gaining more attention due to its advantages associated with low substrate loss and large dimensions compared to silicon wafers. However, the low loss of the substrate and process variation may affect the resonance properties of interconnects. The resonance impacts on signal/power integrity must be analyzed, and mitigation plans should be proposed to maximize the advantages of the glass packaging technology. To analyze the resonance impacts on signal/power integrity, various glass package test vehicles are designed and fabricated. The fabricated test vehicles include transmission lines, PDNs, and patterns to measure an interaction between the through via and PDN. First, transmission line patterns that have 50-ohm characteristic impedance are measured. Due to the process variations, quarter-wave resonances are monitored, and at those frequencies, a sharp increase in insertion loss is observed, which deteriorates the signal integrity of the interconnect. Various PDN patterns are measured in the frequency domain, and regardless of the PDN shape, PDN impedance peaks are observed at the mode resonance frequencies. Due to a low-loss characteristic of the glass substrate, sharp PDN impedance peaks are generated at these frequencies. Also, at these frequencies, both signal and power integrity degradations are measured and analyzed. To fully benefit from the advantages of glass packaging technology, a thorough electrical performance analysis should be conducted to avoid resonances in the target frequency range. Full article

(This article belongs to the Special Issue Microelectronics Assembly and Packaging: Materials and Technologies, 2nd Edition)

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13 pages, 3591 KiB

Open AccessArticle

A Precessing-Coin-Like Rotary Actuator for Distal Endoscope Scanners: Proof-of-Concept Study

by Nirvana Gharib, Mohammad Reza Yousefi Darestani and Kenichi Takahata

Micromachines 2025, 16(1), 111; https://doi.org/10.3390/mi16010111 - 20 Jan 2025

This paper presents, for the first time, a rotary actuator functionalized by an inclined disc rotor that serves as a distal optical scanner for endoscopic probes, enabling side-viewing endoscopy in luminal organs using different imaging/analytic modalities such as optical coherence tomography and Raman [...] Read more.

This paper presents, for the first time, a rotary actuator functionalized by an inclined disc rotor that serves as a distal optical scanner for endoscopic probes, enabling side-viewing endoscopy in luminal organs using different imaging/analytic modalities such as optical coherence tomography and Raman spectroscopy. This scanner uses a magnetic rotor designed to have a mirror surface on its backside, being electromagnetically driven to roll around the cone-shaped hollow base to create a motion just like a precessing coin. An optical probing beam directed from the probe’s optic fiber is passed through the hollow cone to be incident and bent on the back mirror of the rotating inclined rotor, circulating the probing beam around the scanner for full 360° sideway imaging. This new scanner architecture removes the need for a separate prism mirror and holding mechanics to drastically simplify the scanner design and thus, potentially enhancing device miniaturization and reliability. The first proof-of-concept is developed using 3D printing and experimentally analyzed to reveal the ability of both angular stepping at 45° and high-speed rotation up to 1500 rpm within the biologically safe temperature range, a key function for multimodal imaging. Preliminary optical testing demonstrates continuous circumferential scanning of the laser beam with no blind spot caused by power leads to the actuator. The results indicate the fundamental feasibility of the developed actuator as an endoscopic distal scanner, a significant step to further development toward advancing optical endoscope technology. Full article

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

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20 pages, 24743 KiB

Open AccessArticle

Investigation of Chip Morphology in Elliptical Vibration Micro-Turning of Silk Fibroin

by Zhengjian Wang, Xichun Luo, Jining Sun, Wenkun Xie, Yinchuan Piao, Yonghang Jiang and Xiuyuan Chen

Micromachines 2025, 16(1), 110; https://doi.org/10.3390/mi16010110 - 19 Jan 2025

Silk fibroin, known for its biocompatibility and biodegradability, holds significant promise for biomedical applications, particularly in drug delivery systems. The precise fabrication of silk fibroin particles, specifically those ranging from tens of nanometres to hundreds of microns, is critical for these uses. This [...] Read more.

Silk fibroin, known for its biocompatibility and biodegradability, holds significant promise for biomedical applications, particularly in drug delivery systems. The precise fabrication of silk fibroin particles, specifically those ranging from tens of nanometres to hundreds of microns, is critical for these uses. This study introduces elliptical vibration micro-turning as a method for producing silk fibroin particles in the form of cutting chips to serve as carriers for drug delivery systems. A hybrid finite element and smoothed particle hydrodynamics (FE-SPH) model was used to investigate how vibration parameters, such as frequency and amplitude, influence chip formation and morphology. This research is essential for determining the size and shape of silk fibroin particles, which are crucial for their effectiveness in drug delivery systems. The results demonstrate the superior capability of elliptical vibration micro-turning for producing shorter, spiral-shaped chips in the size range of tens of microns, in contrast to the long, continuous chips with zig-zag folds and segmented edges generated by conventional micro-turning. The unique zig-zag shapes result from the interplay between the high flexibility and hierarchical structure of silk fibroin and the controlled cutting environment provided by the diamond tool. Additionally, higher vibration frequencies and lower vertical amplitudes promote chip curling, facilitate breakage, and improve chip control, while reducing cutting forces. Experimental trials further validate the accuracy of the hybrid model. This study represents a significant advancement in the processing of silk fibroin film, offering a complementary approach to fabricating short, spiral-shaped silk fibroin particles with a high surface-area-to-volume ratio compared to traditional spheroids, which holds great potential for enhancing drug-loading efficiency in high-precision drug delivery systems. Full article

(This article belongs to the Special Issue Advances in Digital Manufacturing and Nano Fabrication)

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12 pages, 4448 KiB

Open AccessArticle

Research on Envelope Profile of Lithium Niobate on Insulator Stepped-Mode Spot Size Converter

by Jianfeng Bao, Dengcai Yang, Zhiyu Chen, Jingyuan Zhang and Feng Yang

Micromachines 2025, 16(1), 109; https://doi.org/10.3390/mi16010109 - 19 Jan 2025

To enhance the end-face coupling efficiency of lithium niobate on insulator (LNOI) chips, in conjunction with current device fabrication processes, a stepped spot size converter (SSC) based on a special outer envelope profile has been proposed and investigated. This stepped SSC can reduce [...] Read more.

To enhance the end-face coupling efficiency of lithium niobate on insulator (LNOI) chips, in conjunction with current device fabrication processes, a stepped spot size converter (SSC) based on a special outer envelope profile has been proposed and investigated. This stepped SSC can reduce the coupling loss between the LNOI waveguide and a normal single-mode optical fiber. First, the output waveguide of a mode converter was proposed and simulated, in which the mode field had the biggest overlapping integral factor with a single-mode fiber (MDF ≈ 9.8 μm). Then, a stepped LNOI waveguide, the basic structure of the mode converter, with three kinds of outer envelope profile, was proposed and analyzed. Through analysis of the impacts of different envelope profiles on mode spot conversion efficiency, the relationship between envelope profile and propagation efficiency was obtained. Additionally, the rule of LNOI stair height variation tendency and the pattern of mode spot conversion efficiency for the multi-step mode spot converter in LNOI were obtained. Ultimately, a stepped SSC with a COS-shaped envelope curve was adopted. When this stepped SSC is coupled to single-mode fiber with a mode-field diameter of 9.8 μm, the coupling efficiency of the TE mode was 95.35% at the wavelength of 1550 nm. Full article

(This article belongs to the Special Issue Optoelectronic Fusion Technology)

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13 pages, 2458 KiB

Open AccessArticle

Temperature-Responsive Hybrid Composite with Zero Temperature Coefficient of Resistance for Wearable Thermotherapy Pads

by Ji-Yoon Ahn, Dong-Kwan Lee, Min-Gi Kim, Won-Jin Kim and Sung-Hoon Park

Micromachines 2025, 16(1), 108; https://doi.org/10.3390/mi16010108 - 19 Jan 2025

Carbon-based polymer composites are widely used in wearable devices due to their exceptional electrical conductivity and flexibility. However, their temperature-dependent resistance variations pose significant challenges to device safety and performance. A negative temperature coefficient (NTC) can lead to overcurrent risks, while a positive [...] Read more.

Carbon-based polymer composites are widely used in wearable devices due to their exceptional electrical conductivity and flexibility. However, their temperature-dependent resistance variations pose significant challenges to device safety and performance. A negative temperature coefficient (NTC) can lead to overcurrent risks, while a positive temperature coefficient (PTC) compromises accuracy. In this study, we present a novel hybrid composite combining carbon nanotubes (CNTs) with NTC properties and carbon black (CB) with PTC properties to achieve a near-zero temperature coefficient of resistance (TCR) at an optimal ratio. This innovation enhances the safety and reliability of carbon-based polymer composites for wearable heating applications. Furthermore, a thermochromic pigment layer is integrated into the hybrid composite, enabling visual temperature indication across three distinct zones. This bilayer structure not only addresses the TCR challenge but also provides real-time, user-friendly temperature monitoring. The resulting composite demonstrates consistent performance and high precision under diverse heating conditions, making it ideal for wearable thermotherapy pads. This study highlights a significant advancement in developing multifunctional, temperature-responsive materials, offering a promising solution for safer and more controllable wearable devices. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in 'Materials and Processing' 2024)

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17 pages, 12970 KiB

Open AccessArticle

Design of Dielectric Elastomer Actuator and Its Application in Flexible Gripper

by Xiaoyu Meng, Jiaqing Xie, Haoran Pang, Wenchao Wei, Jiping Niu, Mingqiang Zhu, Fang Gu, Xiaohuan Fan and Haiyan Fan

Micromachines 2025, 16(1), 107; https://doi.org/10.3390/mi16010107 - 19 Jan 2025

Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to [...] Read more.

Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to realize the function of grasping objects of different shapes. The relationship between the pre-stretch ratio and DEA deformation degree was tested by experiments. Based on the performance test results of the dielectric elastomer (DE), the bending deformation process of DEAs with different shapes was simulated by Finite Element Method (FEM) simulation. DEAs with different shapes were prepared through laser cutting and the relationship between the voltage and the bending angle, and the output force of the DEAs was measured. The result shows that under uniaxial stretching, the deformation of the DEA in the stretching direction gradually increases and decreases in the unstretched direction with the increase in the pre-stretch ratio. Under biaxial stretching, DEA deformation increases with the increase in the pre-stretch ratio. The shape of the DEA has a certain influence on the bending deformation range under the same conditions, and the elliptical DEA has a larger bending deformation range and higher output force compared with the rectangular DEA and the trapezium DEA. The elliptical DEA can produce a bending deformation of 40° and an output force of 37.2 mN at a voltage of 24 kV. The three-finger flexible gripper composed of an elliptical DEA can realize the grasping of a paper cup. Full article

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11 pages, 1773 KiB

Open AccessArticle

Design and Study of a Novel P-Type Junctionless FET for High Performance of CMOS Inverter

by Bin Wang, Ziyuan Tang, Yuxiang Song, Lu Liu, Weitao Yang and Longsheng Wu

Micromachines 2025, 16(1), 106; https://doi.org/10.3390/mi16010106 - 17 Jan 2025

In this paper, a novel p-type junctionless field effect transistor (PJLFET) based on a partially depleted silicon-on-insulator (PD-SOI) is proposed and investigated. The novel PJLFET integrates a buried N+-doped layer under the channel to enable the device to be turned off, leading to [...] Read more.

In this paper, a novel p-type junctionless field effect transistor (PJLFET) based on a partially depleted silicon-on-insulator (PD-SOI) is proposed and investigated. The novel PJLFET integrates a buried N+-doped layer under the channel to enable the device to be turned off, leading to a special work mechanism and optimized performance. Simulation results show that the proposed PJLFET demonstrates an I_on/I_off ratio of more than seven orders of magnitude, with I_on reaching up to 2.56 × 10⁻⁴ A/μm, I_off as low as 3.99 × 10⁻¹² A/μm, and a threshold voltage reduced to −0.43 V, exhibiting excellent electrical characteristics. Furthermore, a new CMOS inverter comprising a proposed PJLFET and a conventional NMOSFET is designed. With the identical geometric dimensions and gate electrode, the pull-up and pull-down driving capabilities of the proposed CMOS are equivalent, showing the potential for application in high-performance chips in the future. Full article

(This article belongs to the Special Issue Recent Advances and Challenges in Nanoscale and Microscale Semiconductor Devices)

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