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14 pages, 826 KB

Open AccessArticle

Electrothermal Actuator Performance Analysis via the Moving Least Square Method

by Yuanhu Gu, Jiansheng Liu, Zhangping You, Longfei Wu and Hao Chen

Micromachines 2026, 17(5), 542; https://doi.org/10.3390/mi17050542 - 28 Apr 2026

Viewed by 142

Abstract

This paper presents a case study demonstrating the use of the moving least square method (MLS) for modeling the mechanical response of an electrothermal microactuator. Under the MLS framework, the governing equations for heat transfer and structural mechanics are discretized across the computational [...] Read more.

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

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

15 pages, 8446 KB

Open AccessArticle

Solvent-Free Synthesis of Covalent Organic Frameworks for High-Performance Room Temperature Ammonia Sensing

by Jiayi Wu, Xinru Zhang, Hongwei Xue, Xiaorui Liang, Lei Zhang and Qiulin Tan

Micromachines 2026, 17(4), 499; https://doi.org/10.3390/mi17040499 - 20 Apr 2026

Viewed by 346

Abstract

High-sensitivity rapid detection of ammonia (NH₃) in environmental monitoring, industrial safety, early diagnosis, and other fields is of great significance. Covalent organic frameworks (COFs) have shown great potential in the field of gas sensing due to their designable porous structure and [...] Read more.

High-sensitivity rapid detection of ammonia (NH₃) in environmental monitoring, industrial safety, early diagnosis, and other fields is of great significance. Covalent organic frameworks (COFs) have shown great potential in the field of gas sensing due to their designable porous structure and active sites. However, the traditional solvothermal synthesis method of COFs has problems such as cumbersome steps, high energy consumption and serious environmental pollution. Therefore, it is of great significance to invent a new method for COF synthesis that is green and efficient and makes it easy to conduct flexible ammonia gas sensing. This study first reported a solvent-free synthesis of imine connection 1,3,5-Triformylbenzene (TFB) and p-Phenylenediamine (PDA)—a new strategy for COF. This method innovatively employs zinc trifluoromethyl sulfonate (Zn(OTf)₂) as a bifunctional catalyst. This catalyst not only efficiently catalyzes para-phenylenediamine, but its zinc ions also play a unique structural guiding role, guiding the reactants to be arranged in a directional manner, thereby constructing a highly ordered porous crystal structure. A series of characterizations confirmed that the obtained TFB-PDA-COF had good crystallinity and a high proportion of imine bonds (C=N). The powder material was coated onto a flexible polyimide (PI) substrate, successfully constructing a resistive ammonia gas sensor that operates at room temperature. The test results show that this sensor has a high response value, rapid response/recovery capability, and good selectivity for ammonia gas. More importantly, based on a flexible PI substrate, the device can maintain stable sensing performance even under repeated bending conditions, demonstrating its great potential in practical flexible electronic applications. This work not only provides a brand-new “zinc ion-guided” paradigm for the green and controllable synthesis of COF but also lays a material foundation for their application in the next-generation flexible sensing field. Full article

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

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19 pages, 5230 KB

Open AccessArticle

Global Linearized Sparse Prediction and Adaptive Dead Zone Compensation for a Piezoelectric Actuator

by Xue Qi, Meiting Zhao, Lina Zhang, Lei Fan, Zhihui Liu, Pengying Xu and Qiulin Tan

Micromachines 2026, 17(4), 392; https://doi.org/10.3390/mi17040392 - 24 Mar 2026

Viewed by 258

Abstract

A piezoelectric actuator (PEA) is a fundamental part of a high-precision motion system, yet its performance is critically constrained by inherent nonlinearities such as the velocity dead zone and hysteresis. To overcome these limitations and the associated time-varying dynamics, this study introduces a [...] Read more.

A piezoelectric actuator (PEA) is a fundamental part of a high-precision motion system, yet its performance is critically constrained by inherent nonlinearities such as the velocity dead zone and hysteresis. To overcome these limitations and the associated time-varying dynamics, this study introduces a novel control framework for a dual-mode standing wave PEA. The framework integrates a Global Linearized Sparse Prediction (GLSP) model with an Adaptive Kalman Observer-based Model Predictive Control (AKOBMPC) strategy, specifically designed for velocity dead-zone compensation. The GLSP model employs Koopman operator theory to lift the complex, nonlinear electromechanical and contact dynamics into a linear invariant subspace. Incorporated with a deep learning-based structured pruning mechanism, the model achieves an effective balance between prediction accuracy and computational efficiency, facilitating real-time implementation. Leveraging this high-fidelity model, the AKOBMPC algorithm is developed to estimate unmeasurable disturbances and optimize the control sequence for precise velocity tracking. Experimental results demonstrate the GLSP model’s accurate prediction of system behavior under varying loads and excitation frequencies. The proposed controller effectively suppresses the velocity dead zone, achieving tracking errors within ±0.35 mm/s for a 40.00 mm/s trapezoidal reference and within ±0.50 mm/s for sinusoidal tracking. These results confirm the superior performance of the AKOBMPC scheme over conventional methods, offering a robust solution for high-precision velocity regulation in PEA system and contributing to the advancement of next-generation precision actuator. Full article

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

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17 pages, 2312 KB

Open AccessArticle

Green Nanoparticles for Enhanced Electrochemical Monitoring of Pharmaceutical Contaminants: Comparative Investigation Between Monometallic and Bimetallic Nanoparticles

by Soumaya Nasri, Amani Chrouda, Shazalia Mahmoud Ahmed Ali, Bakheit Mustafa, Manahil Babiker Elamin, Laila M. Alhaidari, Hamdi Ben Halima and Nicole Jafezic-Renault

Micromachines 2026, 17(1), 60; https://doi.org/10.3390/mi17010060 - 31 Dec 2025

Viewed by 655

Abstract

Study presents a comparative analytical investigation into the green synthesis of monometallic and bimetallic nanoparticles using Punica granatum (pomegranate) extract, aimed at developing high-performance electrochemical sensors for the detection of ciprofloxacin (CIP) as a representative pharmaceutical pollutant. Three nanoparticle systems were successfully synthesized: [...] Read more.

Study presents a comparative analytical investigation into the green synthesis of monometallic and bimetallic nanoparticles using Punica granatum (pomegranate) extract, aimed at developing high-performance electrochemical sensors for the detection of ciprofloxacin (CIP) as a representative pharmaceutical pollutant. Three nanoparticle systems were successfully synthesized: monometallic Au@NPs and TiO₂@NPs, as well as the bimetallic AuTiO₂@NPs. Their structural and physicochemical characteristics were comprehensively analyzed using UV–Vis spectroscopy, FTIR, SEM, TEM, and XRD techniques. The obtained nanoparticles exhibited predominantly spherical morphologies with average particle sizes of approximately 40 ± 5 nm for Au@NPs, 50 ± 7 nm for TiO₂@NPs, and 60 ± 6 nm for AuTiO₂@NPs. These nanomaterials were subsequently employed to modify electrode surfaces for electrochemical sensing applications. Their analytical performance was evaluated using cyclic voltammetry (CV) and square-wave voltammetry (SWV). The sensors displayed excellent sensitivity, with limits of detection of 0.8 ppb for TiO₂@NPs, 0.8 ppb for Au@NPs, and 0.2 ppb for the AuTiO₂@NP-based sensor. The bimetallic platform demonstrated superior electrochemical behavior, enhanced signal intensity, and strong selectivity, achieving recovery rates of 98% in tap water and 103% in wastewater. Overall, the results confirm the effectiveness of green-synthesized bimetallic nanoparticles as efficient, low-cost materials for environmental monitoring of emerging pharmaceutical contaminants. Full article

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

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11 pages, 1580 KB

Open AccessArticle

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

by Jingui Zhang and Chuan Wu

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

Viewed by 994

Abstract

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

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

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

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21 pages, 5410 KB

Open AccessArticle

Design and Control of the Manipulator of Magnetic Surgical Forceps with Cable Transmission

by Jingwu Li and Zhijun Sun

Micromachines 2025, 16(6), 650; https://doi.org/10.3390/mi16060650 - 29 May 2025

Cited by 1 | Viewed by 1462

Abstract

Magnetically actuated medical robots have attracted growing research interest because magnetic force can transmit power in a non-contact manner to fix magnetic surgical instruments onto the inner wall of the abdominal cavity. In this paper, we present magnetic and cable-driven surgical forceps with [...] Read more.

Magnetically actuated medical robots have attracted growing research interest because magnetic force can transmit power in a non-contact manner to fix magnetic surgical instruments onto the inner wall of the abdominal cavity. In this paper, we present magnetic and cable-driven surgical forceps with cable transmission. The design achieves significant diameter reduction in the manipulator by separating the power sources (micro-motors) from the manipulator through cable transmission, consequently improving surgical maneuverability. The manipulator adopting cable transmission mechanism has the problem of joint motion coupling. Additionally, due to the compact space within the magnetic surgical forceps, it is difficult to install pre-tightening or decoupling mechanisms. To address these technical challenges, we designed a pair of miniature pre-tensioning buckles for connecting and pre-tensioning the driving cables. A mathematical model was established to characterize the length changes of the coupled joint-driving cables with the angles of moving joints and was integrated into the control program of the manipulator. Joint motion decoupling was achieved through real-time compensation of the length changes of the coupled joint-driving cables. The decoupling and control effects of the manipulator have been verified experimentally. While one joint moves, the angle changes of the coupled joints are within 2°. Full article

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

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12 pages, 1851 KB

Open AccessArticle

Preliminary Monitoring and Observation of Fuel Cell Temperature Characteristics by Using NiCr-NiSi Thin-Film Thermocouple

by Zhihui Liu, Bohao Chang, Jinzhe Li, Yingyu Chen, Xingshu Wang, Zeren Rong, Zixi Wang and Wanyu Ding

Micromachines 2025, 16(6), 639; https://doi.org/10.3390/mi16060639 - 28 May 2025

Cited by 1 | Viewed by 3229

Abstract

This study presents the calibration methodology of NiCr-NiSi thin-film thermocouples and evaluates their application in real-time temperature monitoring and characterization of fuel cell thermal behavior. Experimental results reveal that the Seebeck coefficients of the NiCr-NiSi thin films remain stable after multiple calibration cycles, [...] Read more.

This study presents the calibration methodology of NiCr-NiSi thin-film thermocouples and evaluates their application in real-time temperature monitoring and characterization of fuel cell thermal behavior. Experimental results reveal that the Seebeck coefficients of the NiCr-NiSi thin films remain stable after multiple calibration cycles, indicating good reliability and repeatability. Furthermore, the thermocouples demonstrate an ultrafast response time of less than 15 microseconds and reach thermal equilibrium within 200 microseconds under transient thermal inputs. These characteristics enable accurate and rapid temperature measurement of fuel cell plates up to 100 °C, which is critical for maintaining the safe and efficient operation of fuel cells. Full article

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

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15 pages, 6002 KB

Open AccessArticle

Effect of Flow Length on Pressure and Measurement of PEMFC Temperature by Using Thin-Film Thermocouples

by Huijin Guo, Zhihui Liu, Xingyu Li, Xingshu Wang, Maopeng Zhang, Shiqi Zhang, Zixi Wang and Wanyu Ding

Micromachines 2025, 16(5), 535; https://doi.org/10.3390/mi16050535 - 29 Apr 2025

Cited by 2 | Viewed by 883

Abstract

Based on the COMSOL simulation software (v.6.1), this paper systematically investigates the influence law of runner length on the velocity and pressure distribution of cathode and anode gas runners in proton exchange membrane fuel cells (PEMFCs), and experimentally verifies the measurement effect of [...] Read more.

Based on the COMSOL simulation software (v.6.1), this paper systematically investigates the influence law of runner length on the velocity and pressure distribution of cathode and anode gas runners in proton exchange membrane fuel cells (PEMFCs), and experimentally verifies the measurement effect of thin-film thermocouples on the operating temperature of PEMFCs. The simulation results show that the maximum pressure of the cathode and anode increases nonlinearly with the increase in the runner length, while the velocity distribution remains stable; the shortening of the runners significantly reduces the friction loss along the flow path and optimizes the matching of the permeability of the porous medium. In addition, the NiCr/NiSi thin-film thermocouple prepared by magnetron sputtering exhibits high accuracy (Seebeck coefficient of 41.56 μV/°C) in static calibration and successfully captures the dynamic response characteristics of temperature in PEMFC operation. This study provides a theoretical basis and experimental support for the optimization of fuel cell flow channel design and temperature monitoring technology. Full article

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

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23 pages, 6425 KB

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

Cited by 1 | Viewed by 1722

Abstract

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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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

Cited by 1 | Viewed by 880

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)

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23 pages, 3146 KB

Open AccessArticle

Design of Temperature Monitoring and Fault Warning System for Lithium Ternary Battery Case

by Xiyao Liu and Kuihua Han

Micromachines 2025, 16(3), 345; https://doi.org/10.3390/mi16030345 - 19 Mar 2025

Cited by 2 | Viewed by 2162

Abstract

To enhance the safety of lithium ternary battery cases in new energy vehicles, this study designed a temperature monitoring and fault warning system based on NiCr/NiSi thin-film thermocouples. The system integrates six modules—sensor, amplifier, data acquisition, microprocessor (using the KPCA nonlinear dimensionality reduction [...] Read more.

To enhance the safety of lithium ternary battery cases in new energy vehicles, this study designed a temperature monitoring and fault warning system based on NiCr/NiSi thin-film thermocouples. The system integrates six modules—sensor, amplifier, data acquisition, microprocessor (using the KPCA nonlinear dimensionality reduction algorithm), communication and monitoring, and alarm control—to monitor temperature, voltage, and humidity changes in real time. Multi-level warning thresholds are established (e.g., Level 1: initial temperature 35–55 °C rising to 42–65 °C after 10 min; initial voltage 400–425 V dropping to 398–375 V after 10 min). Experimental results demonstrate that the NiCr/NiSi thermocouple exhibits high sensitivity (average Seebeck coefficient: 41.42 μV/°C) and low repeatability error (1.04%), with a dense and uniform surface structure (roughness: 3.2–5.75 nm). The warning logic, triggered in four levels based on dynamic temperature and voltage changes, achieves an 80% accuracy rate and a low false/missed alarm rate of 4%. Long-term operation tests show stable monitoring deviations (±0.2 °C for temperature and ±0.02 V for voltage over 24 h). The system also adapts to varying humidity environments, with peak sensitivity (41.3 μV/°C) at 60% RH. This research provides a highly reliable solution for battery safety management in new energy vehicles. Full article

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

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17 pages, 5039 KB

Open AccessArticle

Optimization of Parameters and Comparison of Detection Signals for Planar Coil Particle Detection Sensors with Different Core Materials

by Changzhi Gu, Chao Liu, Bo Liu, Wenbo Zhang, Chenzhao Bai, Chenyong Wang, Yuqing Sun and Hongpeng Zhang

Micromachines 2024, 15(12), 1520; https://doi.org/10.3390/mi15121520 - 20 Dec 2024

Cited by 1 | Viewed by 1715

Abstract

The cleanliness of lubricating oil plays a key role in determining the operational health of mechanical systems, serving as a critical metric that delineates the extent of equipment wear. In this study, we present a magnetic-core-type planar coil particle detection sensor. The detection [...] Read more.

The cleanliness of lubricating oil plays a key role in determining the operational health of mechanical systems, serving as a critical metric that delineates the extent of equipment wear. In this study, we present a magnetic-core-type planar coil particle detection sensor. The detection accuracy and detection limit are improved by optimizing the magnetic field inside the sensor. The optimization of the magnetic field is achieved through the finite element simulation analysis of the coil and the magnetic core. First, the finite element simulation software COMSOL 6.0 is used to model the sensor in three dimensions (3D). Then, we study the distribution of the magnetic field under different coil radii, core conductivity levels, and other parameters. We obtain the sensor structure after optimizing the magnetic field. The sensor is made using experimental methods, and the iron particles and copper particles are detected. The results show that the lower limit of detection of iron particles can reach 46 μm, and the lower limit of detection of copper particles can reach 110 μm. Full article

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

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16 pages, 6182 KB

Open AccessArticle

Electrostatic MEMS Two-Dimensional Scanning Micromirrors Integrated with Piezoresistive Sensors

by Yameng Shan, Lei Qian, Kaixuan He, Bo Chen, Kewei Wang, Wenchao Li and Wenjiang Shen

Micromachines 2024, 15(12), 1421; https://doi.org/10.3390/mi15121421 - 26 Nov 2024

Cited by 11 | Viewed by 4954

Abstract

The MEMS scanning micromirror requires angle sensors to provide real-time angle feedback during operation, ensuring a stable and accurate deflection of the micromirror. This paper proposes a method for integrating piezoresistive sensors on the torsion axis of electrostatic MEMS micromirrors to detect the [...] Read more.

The MEMS scanning micromirror requires angle sensors to provide real-time angle feedback during operation, ensuring a stable and accurate deflection of the micromirror. This paper proposes a method for integrating piezoresistive sensors on the torsion axis of electrostatic MEMS micromirrors to detect the deflection angle. The design uses a multi-layer bonding process to realize a vertical comb-driven structure. The device structure is designed as a double-layer structure, in which the top layer is the ground layer and integrates with piezoresistive sensor. This approach avoids crosstalk between the applied drive voltage and the piezoresistive sensor. This design also optimizes the sensor’s size, improving sensitivity. A MEMS two-dimensional (2D) scanning micromirror with a 1 mm mirror diameter was designed and fabricated. The test results indicated that, in a vacuum environment, the torsional resonance frequencies of the micromirror’s fast axis and slow axis were 17.68 kHz and 2.225 kHz, respectively. When driving voltages of 33 V and 40 V were applied to the fast axis and slow axis of the micromirror, the corresponding optical scanning angles were 55° and 45°, respectively. The piezoresistive sensor effectively detects the micromirror’s deflection state, and optimizing the sensor’s size achieved a sensitivity of 13.87 mV/V/°. The output voltage of the piezoresistive sensor shows a good linear relationship with the micromirror’s deflection angle, enabling closed-loop feedback control of the electrostatic MEMS micromirror. Full article

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

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13 pages, 2526 KB

Open AccessArticle

A Novel Nano-Spherical Tip for Improving Precision in Elastic Modulus Measurements of Polymer Materials via Atomic Force Microscopy

by Tianyu Fu, Paul C. Uzoma, Xiaolei Ding, Pengyuan Wu, Oleksiy Penkov and Huan Hu

Micromachines 2024, 15(9), 1175; https://doi.org/10.3390/mi15091175 - 22 Sep 2024

Cited by 6 | Viewed by 3617

Abstract

Micro-nano-scale mechanical properties are vital for engineering and biological materials. The elastic modulus is generally measured by processing the force–indentation curves obtained by atomic force microscopy (AFM). However, the measurement precision is largely affected by tip shape, tip wear, sample morphology, and the [...] Read more.

Micro-nano-scale mechanical properties are vital for engineering and biological materials. The elastic modulus is generally measured by processing the force–indentation curves obtained by atomic force microscopy (AFM). However, the measurement precision is largely affected by tip shape, tip wear, sample morphology, and the contact model. In such research, it has been found that the radius of the sharp tip increases due to wear during contact scanning, affecting elastic modulus calculations. For flat-ended tips, it is difficult to identify the contact condition, leading to inaccurate results. Our research team has invented a nano-spherical tip, obtained by implanting focused helium ions into a silicon microcantilever, causing it to expand into a silicon nanosphere. This nano-spherical tip has the advantages of sub-micro size and a smooth spherical surface. Comparative tests of the elastic modulus measurement were conducted on polytetrafluoroethylene (PTFE) and polypropylene (PP) using these three tips. Overall, the experimental results show that our nano-spherical tip with a consistent tip radius, symmetrical geometric shape, and resistance to wear and contamination can improve precision in elastic modulus measurements of polymer materials. Full article

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

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Review

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50 pages, 4972 KB

Open AccessReview

Wall Thinning Monitoring in Boiler U-Bends: A Review and Future Prospects with Fiber Optic Sensing

by Aayush Madan, Wenyu Jiang, Yixin Wang, Yaowen Yang, Jianzhong Hao and Perry Ping Shum

Micromachines 2026, 17(5), 566; https://doi.org/10.3390/mi17050566 - 1 May 2026

Viewed by 132

Abstract

Tube boilers are extensively employed in oil and gas refineries, as well as in petroleum, energy, and power generation industries, where they serve critical functions in local steam-generation units and combined-cycle gas turbine (CCGT) plants. However, these boilers are prone to defects arising [...] Read more.

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

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

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