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Magnetic Polymeric Conduits in Biomedical Applications
Design and Study of a Novel P-Type Junctionless FET for High Performance of CMOS Inverter
An All-in-One Testing Chip for Simultaneous Measurement of Multiple Thermoelectric Parameters in Doped Polysilicon
Automatic Extraction and Compensation of P-Bit Device Variations in Large Array Utilizing Boltzmann Machine Training

Journal Description

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 (Instruments and Instrumentation) / CiteScore - Q2 (Electrical and Electronic 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

17 pages, 9262 KiB

Open AccessArticle

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

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

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17 pages, 12485 KiB

Open AccessArticle

Research and Experimentation on Acoustic Monitoring Technology for Laser Drilling Penetration

by Bowen Lian, Kewen Pan, Liqun Wang, Liwu Shi, Jianhua Yao and Wei Guo

Micromachines 2025, 16(4), 475; https://doi.org/10.3390/mi16040475 - 16 Apr 2025

To prevent back wall damage in cavity workpieces during laser drilling, it is crucial to monitor hole penetration status in real time. This study proposes a laser drilling penetration monitoring method based on acoustic principles. First, the acoustic module parameters of the system [...] Read more.

To prevent back wall damage in cavity workpieces during laser drilling, it is crucial to monitor hole penetration status in real time. This study proposes a laser drilling penetration monitoring method based on acoustic principles. First, the acoustic module parameters of the system were simulated and calibrated using COMSOL Multiphysics (version 6.1) software, resulting in an optimal sound source frequency of 35 kHz and an incident angle of 30° for the acoustic waves. Next, a nickel-based alloy laser drilling acoustic monitoring platform was designed and constructed, and the system’s upper computer control software was developed. Subsequent drilling trials were performed on the validated platform. During the experiments, the threshold for hole penetration signals under the specified experimental parameters was determined, enabling the acquisition of acoustic signals and the identification of hole penetration status. Furthermore, a correlation between the intensity of the acoustic signals and the exit aperture of the drilled holes was established. The results demonstrate the feasibility of using acoustic principles to monitor hole penetration status and measure machining aperture, providing both theoretical and experimental foundations for active laser drilling to prevent back wall damage. Full article

(This article belongs to the Special Issue Optical and Laser Material Processing, 2nd Edition)

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27 pages, 16472 KiB

Open AccessReview

Recent Research on Structural Design, Performance Optimization, and Applications of Piezoelectric Pumps

by Qiufeng Yan, Zhiling Liu, Le Wang, Wanting Sun and Mengyao Jiang

Micromachines 2025, 16(4), 474; https://doi.org/10.3390/mi16040474 - 16 Apr 2025

With the advantages of simple structure, low power consumption, no electromagnetic interference, and fast response, piezoelectric pumps (PPs) have been widely used in the fields of chip cooling, biomedical applications, chemical applications, and fuel supply applications. In recent decades, scholars have proposed various [...] Read more.

With the advantages of simple structure, low power consumption, no electromagnetic interference, and fast response, piezoelectric pumps (PPs) have been widely used in the fields of chip cooling, biomedical applications, chemical applications, and fuel supply applications. In recent decades, scholars have proposed various PPs, and this article reviews the recent research results. In this review, according to the “valve” structure, PPs are divided into valve-less piezoelectric pumps (VLPPs), valve-based piezoelectric pumps (VBPPs), and piezoelectric pumps with valve and valve-less state transitions (PPVVSTs). Firstly, the design methods of typical structures were discussed, and comparisons were made in terms of driving frequency, driving voltage, output pressure, flow rate, structure materials, and pump size. The advantages and disadvantages of VLPPs, VBPPs, and PPVVSTs were analyzed. Then, we compared the driving parameters, output performance, structure materials, and pump size of single-chamber piezoelectric pumps (SCPs) and multi-chamber piezoelectric pumps (MCPs) and analyzed the advantages and disadvantages of SCPs and MCPs. Optimization methods proposed in recent years have been summarized to address the issues of the cavitation phenomenon, the liquid back-flow problem, and low output performance in PPs. Subsequently, the application research of PPs and the distribution of academic achievements were discussed. Finally, this review was summarized, and future research hot spots for PPs were proposed. The main contribution of this review is to provide piezoelectric pump (PP) researchers with a certain understanding of the structural design, optimization methods, practical applications, and research distribution of PPs, which can provide theoretical guidance for future research. Full article

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

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12 pages, 6694 KiB

Open AccessArticle

Normally Off AlGaN/GaN MIS-HEMTs with Self-Aligned p-GaN Gate and Non-Annealed Ohmic Contacts via Gate-First Fabrication

by Yinmiao Yin, Qian Fan, Xianfeng Ni, Chao Guo and Xing Gu

Micromachines 2025, 16(4), 473; https://doi.org/10.3390/mi16040473 - 16 Apr 2025

This study introduces an enhancement-mode AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) featuring a self-aligned p-GaN gate structure, fabricated using a gate-first process. The key innovation of this work lies in simplifying the fabrication process by utilizing gate metallization for both electrical contact and etching [...] Read more.

This study introduces an enhancement-mode AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) featuring a self-aligned p-GaN gate structure, fabricated using a gate-first process. The key innovation of this work lies in simplifying the fabrication process by utilizing gate metallization for both electrical contact and etching mask functions, enabling precise self-alignment. A highly selective Cl₂/N₂/O₂ inductively coupled plasma (ICP) etching process was optimized to etch the p-GaN layer in the access regions, with a selectivity ratio of 33:1 and minimal damage to the AlGaN barrier. Additionally, a novel, non-annealed ohmic contact formation technique was developed, leveraging ICP etching to create nitrogen vacancies that facilitate contact formation without requiring thermal annealing. This technique streamlines the process by combining ohmic contact formation and mesa isolation into a single lithographic step. Incorporating a SiNx gate dielectric layer led to a 4.5 V threshold voltage shift in the fabricated devices. The resulting devices exhibited improved electrical performance, including a wide gate voltage swing (>10 V), a high on/off current ratio (~10⁷), and clear pinch-off characteristics. These results demonstrate the effectiveness of the proposed fabrication approach, offering significant improvements in process efficiency and manufacturability. Full article

(This article belongs to the Special Issue GaN Heterostructure Devices: From Materials to Application, 2nd Edition)

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41 pages, 7054 KiB

Open AccessReview

Seeking Solutions for Inclusively Economic, Rapid, and Safe Molecular Detection of Respiratory Infectious Diseases: Comprehensive Review from Polymerase Chain Reaction Techniques to Amplification-Free Biosensing

by Yaping Xie, Zisheng Zong, Qin Jiang, Xingxing Ke and Zhigang Wu

Micromachines 2025, 16(4), 472; https://doi.org/10.3390/mi16040472 - 15 Apr 2025

Frequent outbreaks of respiratory infectious diseases, driven by diverse pathogens, have long posed significant threats to public health, economic productivity, and societal stability. Respiratory infectious diseases are highly contagious, characterized by short incubation periods, diverse symptoms, multiple transmission routes, susceptibility to mutations, and [...] Read more.

Frequent outbreaks of respiratory infectious diseases, driven by diverse pathogens, have long posed significant threats to public health, economic productivity, and societal stability. Respiratory infectious diseases are highly contagious, characterized by short incubation periods, diverse symptoms, multiple transmission routes, susceptibility to mutations, and distinct seasonality, contributing to their propensity for outbreaks. The absence of effective antiviral treatments and the heightened vulnerability of individuals with weakened immune systems make them more susceptible to infection, with severe cases potentially leading to complications or death. This situation becomes particularly concerning during peak seasons, such as influenza outbreaks. Therefore, early detection, diagnosis, and treatment are critical, alongside the prevention of cross-infection, ensuring patient safety, and controlling healthcare costs. To address these challenges, this review aims to identify a comprehensive, rapid, safe, and cost-effective diagnostic approach for respiratory infectious diseases. This approach is framed within the existing hierarchical healthcare system, focusing on establishing diagnostic capabilities at hospitals, community, and home levels to effectively tackle the above issues. In addition to PCR and isothermal amplification, the review also explores emerging molecular diagnostic strategies that may better address the evolving needs of respiratory disease diagnostics. A key focus is the transition from amplification technologies to amplification-free biosensing approaches, with particular attention given to their potential for home-based testing. This shift seeks to overcome the limitations of conventional amplification methods, particularly in decentralized and home diagnostics, offering a promising solution to enhance diagnostic speed and safety during outbreaks. In the future, with the integration of AI technologies into molecular amplification technologies, biosensors, and various application levels, the inclusively economic, rapid, and safe respiratory disease diagnosis solutions will be further optimized, and their accessibility will become more widespread. Full article

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

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12 pages, 3517 KiB

Open AccessArticle

High-Efficiency Wireless Power Transfer System Based on Low-Frequency AlScN Piezoelectric Micromechanical Ultrasonic Transducers for Implantable Medical Devices

by Wanyun Cui, Jianwei Zong, Junxiang Li, Qiang Ping, Lei Qiu and Liang Lou

Micromachines 2025, 16(4), 471; https://doi.org/10.3390/mi16040471 - 15 Apr 2025

In recent years, implantable medical devices (IMDs) have introduced groundbreaking solutions for managing various health conditions. However, traditional implanted batteries necessitate periodic surgical replacement and tend to be relatively bulky, posing significant inconvenience to patients. To overcome these limitations, researchers have investigated various [...] Read more.

In recent years, implantable medical devices (IMDs) have introduced groundbreaking solutions for managing various health conditions. However, traditional implanted batteries necessitate periodic surgical replacement and tend to be relatively bulky, posing significant inconvenience to patients. To overcome these limitations, researchers have investigated various wireless power transfer (WPT) techniques, among which the ultrasonic wireless power transmission (UWPT) technique has distinct advantages. However, limited research has been conducted on ultrasonic power transfer at lower operating frequencies. Therefore, this study explores wireless power transfer using scandium-doped aluminum nitride (AlScN) piezoelectric micro-electromechanical transducers (PMUTs) in deionized (DI) water. Experimental results indicate that at an operating frequency of 14.075 kHz, the power transfer efficiency (PTE) can reach up to 2.68% under optimal load resistance conditions. Furthermore, a low-frequency UWPT system based on a AlScN PMUT has been developed, delivering a stable 3.3 V output for implantable medical devices and contributing to the advancement of a full-spectrum UWPT framework. Full article

(This article belongs to the Section A：Physics)

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16 pages, 5056 KiB

Open AccessArticle

Prognostic Value of the Number of Circulating Tumor Cells in Patients with Metastatic Non-Small Cell Lung Cancer

by Arthur B. Volovetsky, Victoria A. Novikova, Anastasia Boloban, Aleksej S. Rzhevskiy, Alina Kapitannikova, Elena G. Ovchinnikova, Tatjana P. Klejmentjeva, Vladislav A. Grishin, Yana Pigareva, Andrei V. Zvyagin, Majid Ebrahimi Warkiani and Anna V. Maslennikova

Micromachines 2025, 16(4), 470; https://doi.org/10.3390/mi16040470 - 15 Apr 2025

Investigating the molecular and genetic characteristics of circulating tumor cells (CTCs) presents a promising approach for personalizing treatment in patients with malignant neoplasms, given the limitations of traditional biopsy and histopathology. This study aimed to isolate, characterize, and analyze CTC dynamics in the [...] Read more.

Investigating the molecular and genetic characteristics of circulating tumor cells (CTCs) presents a promising approach for personalizing treatment in patients with malignant neoplasms, given the limitations of traditional biopsy and histopathology. This study aimed to isolate, characterize, and analyze CTC dynamics in the peripheral blood of 30 patients with metastatic lung cancer to develop criteria for treatment response and prognosis. We detected CTCs before the start of the treatment and monitored changes during treatment, correlating these with responses evaluated by standard imaging methods. A decrease in the CTCs in the course of the therapy was linked to a favorable tumor response, while the stable CTC counts indicated a lack of response and poor survival prognosis. The OS of patients was analyzed and compared with the initial number of CTCs in peripheral blood samples. The significant reductions in median OS were evident in patients with >3 total CTCs at baseline compared to those with ≤3 total CTCs (median survival 26 months, n = 10, vs. median survival 8 months, n = 19, respectively with HR = 2.6, 95% CI 1.07 to 6.4). Full article

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

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16 pages, 3089 KiB

Open AccessArticle

Backstepping Controller for Nanopositioning in Piezoelectric Actuators with ANN Hysteresis Compensation

by Asier del Rio, Oscar Barambones, Eneko Artetxe, Jokin Uralde and Isidro Calvo

Micromachines 2025, 16(4), 469; https://doi.org/10.3390/mi16040469 - 15 Apr 2025

Piezoelectric actuators (PEAs) are widely used in high-precision applications but suffer from nonlinear hysteresis effects that degrade positioning accuracy. To address this challenge, this study presents a backstepping controller with an Artificial Neural Network (ANN)-based feedforward compensation scheme to enhance trajectory tracking performance. [...] Read more.

Piezoelectric actuators (PEAs) are widely used in high-precision applications but suffer from nonlinear hysteresis effects that degrade positioning accuracy. To address this challenge, this study presents a backstepping controller with an Artificial Neural Network (ANN)-based feedforward compensation scheme to enhance trajectory tracking performance. The ANN compensates for the hysteresis effects, while the backstepping strategy ensures robust reference tracking. The proposed controller is validated through real-time experiments using a piezoelectric actuator system. Comparative analysis with a conventional PID controller demonstrates the superiority of the backstepping approach, achieving significantly lower tracking errors across different reference signals and frequencies. Error metrics have been employed to confirm the improved accuracy and robustness of the proposed method. These findings highlight the effectiveness of the proposed ANN-enhanced backstepping control in overcoming hysteresis-related challenges in precision positioning applications. Full article

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

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12 pages, 8262 KiB

Open AccessArticle

High-Sensitivity and Wide-Range Flexible Pressure Sensor Based on Gradient-Wrinkle Structures and AgNW-Coated PDMS

by Xiaoran Liu, Xinyi Wang, Tao Xue, Yingying Zhao and Qiang Zou

Micromachines 2025, 16(4), 468; https://doi.org/10.3390/mi16040468 - 15 Apr 2025

Flexible pressure sensors have garnered significant attention due to their wide range of applications in human motion monitoring and smart wearable devices. However, the fabrication of pressure sensors that offer both high sensitivity and a wide detection range remains a challenging task. In [...] Read more.

Flexible pressure sensors have garnered significant attention due to their wide range of applications in human motion monitoring and smart wearable devices. However, the fabrication of pressure sensors that offer both high sensitivity and a wide detection range remains a challenging task. In this paper, we propose an AgNW-coated PDMS flexible piezoresistive sensor based on a gradient-wrinkle structure. By modifying the microstructure of PDMS, the sensor demonstrates varying sensitivities and pressure responses across different pressure ranges. The wrinkle microstructure contributes to high sensitivity (0.947 kPa⁻¹) at low pressures, while the PDMS film with a gradient contact height ensures a continuous change in the contact area through the gradual activation of the contact wrinkles, resulting in a wide detection range (10–50 kPa). This paper also investigates the contact state of gradient-wrinkle films under different pressures to further elaborate on the sensor’s sensing mechanism. The sensor’s excellent performance in real-time response to touch behavior, joint motion, swallowing behavior recognition, and grasping behavior detection highlights its broad application prospects in human–computer interaction, human motion monitoring, and intelligent robotics. Full article

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12 pages, 1776 KiB

Open AccessArticle

A Progressive Search Method for Roundness Evaluation Based on Minimum Zone Criterion

by Jian Mei, Binbin Li, Guohua Hu, Chuanzhi Fang, Sheng Zhang, Juan Zheng, Qian Zhang, Lei Hong and Qiangxian Huang

Micromachines 2025, 16(4), 467; https://doi.org/10.3390/mi16040467 - 15 Apr 2025

With the rapid development of micro-machining technology, the feature size of object parts becomes smaller whilst the roundness tolerance must be critically verified at sub-micrometers or nanometers. Therefore, establishing a method is critically important for evaluating roundness errors to guarantee the machining quality. [...] Read more.

With the rapid development of micro-machining technology, the feature size of object parts becomes smaller whilst the roundness tolerance must be critically verified at sub-micrometers or nanometers. Therefore, establishing a method is critically important for evaluating roundness errors to guarantee the machining quality. A progressive search method is proposed based on the minimum zone criterion in the Cartesian coordinate system in this paper. The least-square center of the measured points is used as the initial reference center by establishing a search circle model for progressively approaching the minimum zone circle center. To testify to the feasibility and performance of the proposed method, comparison and simulation experiments are implemented. The results demonstrated that the progressive search method is effective, reliable, and can evaluate roundness error accurately and quickly with not more than 0.1 s and 10 times. Full article

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45 pages, 10822 KiB

Open AccessReview

Progress in CO₂ Gas Sensing Technologies: Insights into Metal Oxide Nanostructures and Resistance-Based Methods

by Yash Ughade, Shubham Mehta, Gautam Patel, Roopa Gowda, Nirav Joshi and Rohan Patel

Micromachines 2025, 16(4), 466; https://doi.org/10.3390/mi16040466 - 14 Apr 2025

The demand for reliable and cost-effective CO₂ gas sensors is escalating due to their extensive applications in various sectors such as food packaging, indoor air quality assessment, and real-time monitoring of anthropogenic CO₂ emissions to mitigate global warming. Nanostructured materials exhibit [...] Read more.

The demand for reliable and cost-effective CO₂ gas sensors is escalating due to their extensive applications in various sectors such as food packaging, indoor air quality assessment, and real-time monitoring of anthropogenic CO₂ emissions to mitigate global warming. Nanostructured materials exhibit exceptional properties, including small grain size, controlled morphology, and heterojunction effects, rendering them promising candidates for chemiresistive CO₂ gas sensors. This review article provides an overview of recent advancements in chemiresistive CO₂ gas sensors based on nanostructured semiconducting materials. Specifically, it discusses single oxide structures, metal-decorated oxide nanostructures, and heterostructures, elucidating the correlations between these nanostructures and their CO₂ sensing properties. Additionally, it addresses the challenges and future prospects of chemiresistive CO₂ gas sensors, aiming to provide insights into the ongoing developments in this field. Full article

(This article belongs to the Special Issue Gas Sensors: From Fundamental Research to Applications)

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23 pages, 6425 KiB

Open AccessArticle

The Feasibility and Performance of Thin-Film Thermocouples in Measuring Insulated Gate Bipolar Transistor Temperatures in New Energy Electric Drives

by Bole Xiang, Guoqiang Li and Zhihui Liu

Micromachines 2025, 16(4), 465; https://doi.org/10.3390/mi16040465 - 14 Apr 2025

In the new energy electric drive system, the thermal stability of IGBT, a core power device, significantly impacts the system’s overall performance. Accurate IGBT temperature measurement is crucial, but traditional methods face limitations in IGBT’s compact working space. Thin-film thermocouples, with their thin [...] Read more.

In the new energy electric drive system, the thermal stability of IGBT, a core power device, significantly impacts the system’s overall performance. Accurate IGBT temperature measurement is crucial, but traditional methods face limitations in IGBT’s compact working space. Thin-film thermocouples, with their thin and light features, offer a new solution. In this study, Ni 90% Cr 10% and Ni 97% Si 3% thin-film thermocouples were prepared on polyimide substrates via magnetron sputtering. After calibration, the Seebeck coefficient of the thin-film thermocouple temperature sensors reached 40.23 μV/°C, and the repeatability error stabilized at about 0.3% as the temperature rose, showing good stability. Researchers studied factors affecting IGBT temperature. Thin-film thermocouples can accurately monitor IGBT module surface temperature under different conditions. Compared to K-type wire thermocouples, they measure slightly higher temperatures. As the control signal’s switching frequency increases, IGBT temperature first rises then falls; as the duty cycle increases, the temperature keeps rising. This is consistent with RAC’s junction temperature prediction theory, validating the feasibility of thin-film thermocouples for IGBT chip temperature measurement. Thin-film thermocouples have great application potential in power device temperature measurement and may be a key research direction, supporting the optimization and upgrading of new energy electric drive systems. Full article

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

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19 pages, 6895 KiB

Open AccessArticle

A Hybrid GRA-TOPSIS-RFR Optimization Approach for Minimizing Burrs in Micro-Milling of Ti-6Al-4V Alloys

by Rongkai Tan, Abhilash Puthanveettil Madathil, Qi Liu, Jian Cheng and Fengtao Lin

Micromachines 2025, 16(4), 464; https://doi.org/10.3390/mi16040464 - 14 Apr 2025

Micro-milling is increasingly recognized as a crucial technique for machining intricate and miniature 3D aerospace components, particularly those fabricated from difficult-to-cut Ti-6Al-4V alloys. However, its practical applications are hindered by significant challenges, particularly the unavoidable generation of burrs, which complicate subsequent finishing processes [...] Read more.

Micro-milling is increasingly recognized as a crucial technique for machining intricate and miniature 3D aerospace components, particularly those fabricated from difficult-to-cut Ti-6Al-4V alloys. However, its practical applications are hindered by significant challenges, particularly the unavoidable generation of burrs, which complicate subsequent finishing processes and adversely affect overall part quality. To optimize the burr formation in the micro-milling of Ti-6Al-4V alloys, this study proposes a novel hybrid-ranking optimization algorithm that integrates Grey Relational Analysis (GRA) with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This approach innovatively combines GRA and TOPSIS with a random forest regression (RFR) model, facilitating the exploration of nonlinear and complex relationships between input parameters and machining outcomes. Specifically, the effects of spindle speed, depth of cut, and feed rate per tooth on surface roughness and burr width generated during both down-milling and up-milling processes were systematically investigated using the proposed methodology. The results reveal that the depth of cut is the most influential factor affecting surface roughness, while feed rate per tooth plays a critical role in controlling burr formation. Moreover, the GRA-TOPSIS-RFR method significantly outperforms existing optimization and prediction models, with the integration of the RFR model enhancing prediction accuracy by 42.6% compared to traditional linear regression approaches. The validation experimental results agree well with the GRA-TOPSIS-RFR-optimized outcomes. This research provides valuable insights into optimizing the micro-milling process of titanium components, ultimately contributing to improved quality, performance, and service life across various aerospace applications. Full article

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

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17 pages, 9524 KiB

Open AccessArticle

Design of an Electronic Nose System with Automatic End-Tidal Breath Gas Collection for Enhanced Breath Detection Performance

by Dongfu Xu, Pu Liu, Xiangming Meng, Yizhou Chen, Lei Du, Yan Zhang, Lixin Qiao, Wei Zhang, Jiale Kuang and Jingjing Liu

Micromachines 2025, 16(4), 463; https://doi.org/10.3390/mi16040463 - 14 Apr 2025

End-tidal breath gases originate deep within the lungs, and their composition is an especially accurate reflection of the body’s metabolism and health status. Therefore, accurate collection of end-tidal breath gases is crucial to enhance electronic noses’ performance in breath detection. Regarding this issue, [...] Read more.

End-tidal breath gases originate deep within the lungs, and their composition is an especially accurate reflection of the body’s metabolism and health status. Therefore, accurate collection of end-tidal breath gases is crucial to enhance electronic noses’ performance in breath detection. Regarding this issue, this study proposes a novel electronic nose system and employs a threshold control method based on exhaled gas flow characteristics to design a gas collection module. The module monitors real-time gas flow with a flow meter and integrates solenoid valves to regulate the gas path, enabling automatic collection of end-tidal breath gas. In this way, the design reduces dead space gas contamination and the impact of individual breathing pattern differences. The sensor array is designed to detect the collected gas, and the response chamber is optimized to improve the detection stability. At the same time, the control module realizes automation of the experiment process, including control of the gas path state, signal transmission, and data storage. Finally, the system is used for breath detection. We employ classical machine learning algorithms to classify breath samples from different health conditions with a classification accuracy of more than 90%, which is better than the accuracy achieved in other studies of this type. This is due to the improved quality of the gas we extracted, demonstrating the superiority of our proposed electronic nose system. Full article

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28 pages, 16516 KiB

Open AccessReview

Recent Advances in Microfluidics-Based Monitoring of Waterborne Pathogens: From Isolation to Detection

by Guohao Xu, Gaozhe Cai, Lijuan Liang, Jianxin Cheng, Lujie Song, Rui Sun, Feng Shen, Bo Liu, Shilun Feng and Jin Zhang

Micromachines 2025, 16(4), 462; https://doi.org/10.3390/mi16040462 - 14 Apr 2025

Waterborne pathogens seriously threaten human life and can cause diarrhea, gastrointestinal disorders, and more serious systemic infections. These pathogens are usually caused by contaminated water sources that contain disease-causing microorganisms, such as bacteria, viruses, and parasites, which cause infection and disease when they [...] Read more.

Waterborne pathogens seriously threaten human life and can cause diarrhea, gastrointestinal disorders, and more serious systemic infections. These pathogens are usually caused by contaminated water sources that contain disease-causing microorganisms, such as bacteria, viruses, and parasites, which cause infection and disease when they enter the human body through drinking water or other means. Due to the wide range of transmission routes and the high potential risk of waterborne pathogens, there is an urgent need for an ultrasensitive, rapid, and specific pathogenic microorganism monitoring platform to meet the critical monitoring needs of some water bodies’ collection points daily monitoring needs. Microfluidics-based pathogen surveillance methods are an important stage towards automated detection through real-time and multi-targeted monitoring, thus enabling a comprehensive assessment of the risk of exposure to waterborne pathogens and even emerging microbial contaminants, and thus better protection of public health. Therefore, this paper reviews the latest research results on the isolation and detection of waterborne pathogens based on microfluidic methods. First, we introduce the traditional methods for isolation and detection of pathogens. Then, we compare some existing microfluidic pathogen isolation and detection methods and finally look forward to some future research directions and applications of microfluidic technology in waterborne pathogens monitoring. Full article

(This article belongs to the Special Issue Integrated Optical, Electrochemical, and Electrical Biomicrofluidics)

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15 pages, 28317 KiB

Open AccessArticle

Flexible Pressure Sensor with Tunable Sensitivity and a Wide Sensing Range, Featuring a Bilayer Porous Structure

by Yunjiang Yin, Yingying Zhao, Tao Xue, Xinyi Wang and Qiang Zou

Micromachines 2025, 16(4), 461; https://doi.org/10.3390/mi16040461 - 13 Apr 2025

Flexible piezoresistive pressure sensors have great potential in wearable electronics due to their simple structure, low cost, and ease of fabrication. Porous polymer materials, with their highly deformable internal pores, effectively expand the sensing range. However, a single-sized pore structure struggles to achieve [...] Read more.

Flexible piezoresistive pressure sensors have great potential in wearable electronics due to their simple structure, low cost, and ease of fabrication. Porous polymer materials, with their highly deformable internal pores, effectively expand the sensing range. However, a single-sized pore structure struggles to achieve both high sensitivity and a broad sensing range simultaneously. In this study, a PDMS-based flexible pressure sensor with a bilayer porous structure (BLPS) was successfully fabricated using clamping compression and a sacrificial template method with spherical sucrose cores. The resulting sensor exhibits highly uniform pore sizes, thereby improving performance consistency. Furthermore, since different pore sizes and thicknesses correspond to varying Young’s moduli, this study achieves tunable sensitivity across a wide pressure range by adjusting the bilayer thickness ratio (maximum sensitivity of

0.063 {kPa}^{- 1}

in the 0–23.6 kPa range, with a pressure response range of 0–654 kPa). The sensor also demonstrates a fast response time (128 ms) and excellent fatigue stability (>10,000 cycles). Additionally, this sensor holds great application potential for facial expression monitoring, joint motion detection, pressure distribution matrices, and Morse code communication. Full article

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

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21 pages, 12826 KiB

Open AccessArticle

HeSARIC: A Heterogeneous Cyber–Physical Robotic Swarm Framework for Structural Health Monitoring with Augmented Reality Representation

by Alireza Fath, Christoph Sauter, Yi Liu, Brandon Gamble, Dylan Burns, Evan Trombley, Sai Krishna Reddy Sathi, Tian Xia and Dryver Huston

Micromachines 2025, 16(4), 460; https://doi.org/10.3390/mi16040460 - 13 Apr 2025

This study proposes a cyber–physical framework for the integration of a heterogeneous swarm of robots, sensors, microrobots, and AR for structural health monitoring and confined space inspection based on the application’s unique challenges. The structural issues investigated are cracks in the walls, deformation [...] Read more.

This study proposes a cyber–physical framework for the integration of a heterogeneous swarm of robots, sensors, microrobots, and AR for structural health monitoring and confined space inspection based on the application’s unique challenges. The structural issues investigated are cracks in the walls, deformation of the structures, and damage to the culverts and devices commonly used in buildings. The PC and augmented reality interfaces are incorporated for human–robot collaboration to provide the necessary information to the human user while teleoperating the robots. The proposed interfaces use edge computing and machine learning to enhance operator interactions and to improve damage detection in confined spaces and challenging environments. The proposed swarm inspection framework is called HeSARIC. Full article

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15 pages, 5294 KiB

Open AccessArticle

Theoretical Analysis and Numerical Simulation Research on the Response of Inertial Switches

by Shaokang Cui, Jiachen Hao, Sen Wang, Fukai Wu and Pengzhao Xu

Micromachines 2025, 16(4), 459; https://doi.org/10.3390/mi16040459 - 13 Apr 2025

This paper focuses on inertial switches, which are vital in multiple fields. A theoretical analysis model based on the spring-mass model was proposed, aiming to acquire the mechanical performance of the inertial switch under different loading conditions and reveal the influence of design [...] Read more.

This paper focuses on inertial switches, which are vital in multiple fields. A theoretical analysis model based on the spring-mass model was proposed, aiming to acquire the mechanical performance of the inertial switch under different loading conditions and reveal the influence of design parameters on its dynamic response. Moreover, a numerical simulation model was established using ADAMS 2019 software. Through a series of orthogonal simulations, the effects of the overload peak value and pulse width on the switch’s characteristics were studied. The comparison between theoretical predictions and numerical results shows good agreement. Furthermore, based on numerical results, binary phase diagrams of the peak value and pulse width were obtained, determining the critical curves involving the overload peak value and pulse width, which provides guidance for the design of inertial switches. Full article

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12 pages, 6973 KiB

Open AccessArticle

Investigation on Electromigration-Induced Failure and Reservoir Effect in AlCu Interconnects

by Yuanxiang Zhang, Guoquan Jiang, Jingbo Zhao and Lihua Liang

Micromachines 2025, 16(4), 458; https://doi.org/10.3390/mi16040458 - 13 Apr 2025

Aluminum–copper alloy (AlCu) is commonly utilized as interconnect material in low-power devices. However, as the size of electronic devices continues to decrease and current density increases, electromigration (EM) has emerged as a significant reliability concern for AlCu interconnects in the microelectronics industry. In [...] Read more.

Aluminum–copper alloy (AlCu) is commonly utilized as interconnect material in low-power devices. However, as the size of electronic devices continues to decrease and current density increases, electromigration (EM) has emerged as a significant reliability concern for AlCu interconnects in the microelectronics industry. In this study, two-level AlCu interconnect structures with a Ti/TiN barrier layer were fabricated using 0.18 μm technology to perform accelerated EM tests. The test samples were subjected to three current levels (1.45 mA, 2.40 mA and 5.30 mA) at three ambient temperatures (200 °C, 225 °C and 250 °C) to investigate the nucleation and evolution of voids during EM degradation and then obtain the mean time to failure (MTTF). The numerical simulation method of atomic density integral (ADI) was used to simulate experimental observations based on the ANSYS platform, considering the coupled effects of electron wind force, stress gradient, temperature gradient, and atomic density gradient. A comparison of the experimental results and numerical simulations proves that the ADI method can be applied successfully to EM failure prediction of AlCu interconnects. Finite element models with different reservoir lengths were built to demonstrate the mechanism of the reservoir effect. The results show that the reservoir can improve the EM lifetime of the interconnect, but there is a critical extension length beyond which increasing extension sizes have no effect on EM lifetime. Full article

(This article belongs to the Topic Advanced Integrated Circuit Design and Application)

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14 pages, 2588 KiB

Open AccessArticle

Accelerated Electro-Optic Switching in Liquid Crystal Devices via Ion Trapping by Dispersed Helical Carbon Nanotubes

by Rajratan Basu and Christian C. Kehr

Micromachines 2025, 16(4), 457; https://doi.org/10.3390/mi16040457 - 12 Apr 2025

Free ion impurities in liquid crystals significantly impact the dynamic electro-optic performance of liquid crystal displays, leading to slow switching times, short-term flickering, and long-term image sticking. These ionic contaminants originate from various sources, including LC cell fabrication, electrode degradation, and organic alignment [...] Read more.

Free ion impurities in liquid crystals significantly impact the dynamic electro-optic performance of liquid crystal displays, leading to slow switching times, short-term flickering, and long-term image sticking. These ionic contaminants originate from various sources, including LC cell fabrication, electrode degradation, and organic alignment layers. This study demonstrates that doping LCs with a small concentration of helical carbon nanotubes effectively reduces free ion concentrations by approximately 70%. The resulting reduction in ionic impurities lowers the rotational viscosity of the LC, facilitating faster electro-optic switching. Additionally, the purified LC exhibits enhanced dielectric anisotropy, further improving its performance in display applications. These findings suggest that helical carbon nanotubes doping offers a promising approach for mitigating ion-related issues in liquid crystals without the need for additional chemical treatments, paving the way for an efficient liquid crystal display technology. Full article

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

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