Pub Date : 2026-01-07DOI: 10.1016/j.sna.2026.117464
Ho Huu Hau , Nguyen Viet Nhat , Luong Thi Theu , Phung Thi Viet Bac , Dinh Van An , Pham Van Thang , Hoang Si Hong , Nguyen Xuan Thai , Nguyen Duc Chien , Nguyen Van Duy , Nguyen Duc Hoa , Chu Manh Hung
For the first time, we report a dual-functional gas sensor based on highly sensitive WS2 nanosheets. The WS2 nanosheets were synthesized through a simple and environmentally friendly liquid-phase exfoliation (LPE) process using a water–ethanol solvent. The exfoliated nanosheets were 2–3 layers thick and exhibited p-type semiconducting behavior. The fabricated sensor showed excellent selectivity toward NO2 at room temperature (RT, 25 °C) and NH3 at 50 °C, with high responses of about 10 and 12–5 ppm NO2 and 500 ppm NH3, respectively. In addition, the sensor demonstrated outstanding short- and long-term stability, along with ultra-low detection limits of 4.7 ppb for NO2 and 253.4 ppb for NH3. These features are crucial for practical device applications. Density functional theory (DFT) calculations further revealed strong adsorption energy, charge transfer, and electronic structure modulation of WS2 upon exposure to NO2 and NH3. Overall, these findings demonstrate that few-layer WS2 nanosheets are highly promising for developing low-power, dual-selective, and scalable gas sensors for low-temperature applications.
{"title":"Highly sensitive and dual-selective gas sensing using WS2 nanosheets for NO2 and NH3 detection at low temperature","authors":"Ho Huu Hau , Nguyen Viet Nhat , Luong Thi Theu , Phung Thi Viet Bac , Dinh Van An , Pham Van Thang , Hoang Si Hong , Nguyen Xuan Thai , Nguyen Duc Chien , Nguyen Van Duy , Nguyen Duc Hoa , Chu Manh Hung","doi":"10.1016/j.sna.2026.117464","DOIUrl":"10.1016/j.sna.2026.117464","url":null,"abstract":"<div><div>For the first time, we report a dual-functional gas sensor based on highly sensitive WS<sub>2</sub> nanosheets. The WS<sub>2</sub> nanosheets were synthesized through a simple and environmentally friendly liquid-phase exfoliation (LPE) process using a water–ethanol solvent. The exfoliated nanosheets were 2–3 layers thick and exhibited p-type semiconducting behavior. The fabricated sensor showed excellent selectivity toward NO<sub>2</sub> at room temperature (RT, 25 °C) and NH<sub>3</sub> at 50 °C, with high responses of about 10 and 12–5 ppm NO<sub>2</sub> and 500 ppm NH<sub>3</sub>, respectively. In addition, the sensor demonstrated outstanding short- and long-term stability, along with ultra-low detection limits of 4.7 ppb for NO<sub>2</sub> and 253.4 ppb for NH<sub>3</sub>. These features are crucial for practical device applications. Density functional theory (DFT) calculations further revealed strong adsorption energy, charge transfer, and electronic structure modulation of WS<sub>2</sub> upon exposure to NO<sub>2</sub> and NH<sub>3</sub>. Overall, these findings demonstrate that few-layer WS<sub>2</sub> nanosheets are highly promising for developing low-power, dual-selective, and scalable gas sensors for low-temperature applications.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117464"},"PeriodicalIF":4.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-07DOI: 10.1016/j.sna.2026.117465
Keqin Xie , Shizheng Jin , Weihuang Cai , Jinlong Wu , Tao Zhen , Yingjie Liao , Yuanyuan Liu
To address the demand for high-performance transparent electrodes in flexible optoelectronics, this study was conducted to fabricate silver mesh transparent electrodes using electrohydrodynamic (EHD) printing technology and to explore their application in organic photodetectors (OPDs). Through systematic optimization of printing parameters and post-processing, silver grids with fine line width and excellent performance were successfully achieved, with a spacing of 150 μm identified as the optimal based on a comprehensive evaluation using the figure of merit (FoM). Furthermore, a PDMS-assisted transfer printing technique was developed to achieve high-fidelity integration of the electrodes onto the device's functional layers. When applied to OPDs, the fabricated electrodes demonstrated significant advantages over conventional solid electrodes, including markedly suppressed dark current, reduced interfacial impedance, and unique dual-side photoresponse capability. These findings indicate that the EHD-printed silver mesh electrodes provide a viable pathway for developing a new generation of flexible and wearable photodetection systems, showcasing broad application prospects.
{"title":"EHD-printed silver mesh electrodes enabling organic photodetectors with low dark current and dual-side photodetection","authors":"Keqin Xie , Shizheng Jin , Weihuang Cai , Jinlong Wu , Tao Zhen , Yingjie Liao , Yuanyuan Liu","doi":"10.1016/j.sna.2026.117465","DOIUrl":"10.1016/j.sna.2026.117465","url":null,"abstract":"<div><div>To address the demand for high-performance transparent electrodes in flexible optoelectronics, this study was conducted to fabricate silver mesh transparent electrodes using electrohydrodynamic (EHD) printing technology and to explore their application in organic photodetectors (OPDs). Through systematic optimization of printing parameters and post-processing, silver grids with fine line width and excellent performance were successfully achieved, with a spacing of 150 μm identified as the optimal based on a comprehensive evaluation using the figure of merit (FoM). Furthermore, a PDMS-assisted transfer printing technique was developed to achieve high-fidelity integration of the electrodes onto the device's functional layers. When applied to OPDs, the fabricated electrodes demonstrated significant advantages over conventional solid electrodes, including markedly suppressed dark current, reduced interfacial impedance, and unique dual-side photoresponse capability. These findings indicate that the EHD-printed silver mesh electrodes provide a viable pathway for developing a new generation of flexible and wearable photodetection systems, showcasing broad application prospects.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117465"},"PeriodicalIF":4.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To address traditional flexible force sensors’ limitations of single-direction force detection and small effective detection area, this study develops a composite flexible force sensor. It integrates Fiber Bragg grating and flexible thin-film array piezoresistive sensors, adopts an adaptive weighted data fusion strategy, and uses silicic acid gel as the encapsulation matrix to layer-encapsulate FBG and piezoresistive sensors with a sensitized structure between layers. The sensor structure was optimized via finite element simulation. After force calibration simulation, samples were fabricated, and full-coverage/localized positive static force experiments were conducted. Results show the sensor has a large effective detection area and detects positive/lateral static forces: FBG layer sensitivity is 0.13 nm/N (positive) and 0.09 nm/N (lateral), piezoresistive layer 81.54/N. Dynamic tests confirm excellent repeatability, response–recovery, and low temperature/humidity susceptibility. The fusion strategy improves accuracy by 25%. The relationship between total sensitivity and structural parameters was studied, revealing the coupled sensor’s total sensitivity is 36.8 /N.
{"title":"Bidirectional flexible composite force sensors based on FBG sensing and piezoresistive sensing principles","authors":"Yuhang Wang, Jiahui Guo, Jindi Guo, Yufu Qin, Zonghai Wu, Tao Zhang","doi":"10.1016/j.sna.2025.117444","DOIUrl":"10.1016/j.sna.2025.117444","url":null,"abstract":"<div><div>To address traditional flexible force sensors’ limitations of single-direction force detection and small effective detection area, this study develops a composite flexible force sensor. It integrates Fiber Bragg grating and flexible thin-film array piezoresistive sensors, adopts an adaptive weighted data fusion strategy, and uses silicic acid gel as the encapsulation matrix to layer-encapsulate FBG and piezoresistive sensors with a sensitized structure between layers. The sensor structure was optimized via finite element simulation. After force calibration simulation, samples were fabricated, and full-coverage/localized positive static force experiments were conducted. Results show the sensor has a large effective detection area and detects positive/lateral static forces: FBG layer sensitivity is 0.13 nm/N (positive) and 0.09 nm/N (lateral), piezoresistive layer 81.54/N. Dynamic tests confirm excellent repeatability, response–recovery, and low temperature/humidity susceptibility. The fusion strategy improves accuracy by 25%. The relationship between total sensitivity and structural parameters was studied, revealing the coupled sensor’s total sensitivity is 36.8 /N.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117444"},"PeriodicalIF":4.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-07DOI: 10.1016/j.sna.2026.117462
Kamalesh Tripathy, Mitradip Bhattacharjee
A highly sensitive, stable, and flexible temperature sensor is in high demand for numerous applications such as robotics, e-skin, healthcare, etc. Flexible sensors are prone to high mechanical stress during the fabrication process as well as during operation. Sensor packaging with proper encapsulation prevents unwanted damage to the sensor, increasing its longevity. Keeping this in mind, we fabricated a flexible polydimethylsiloxane (PDMS) encapsulated temperature sensor on a PET (polyethylene terephthalate) for human body temperature measurement. The active layer for the sensor is a composite of Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), graphene oxide (GO), 3-Glycidyloxypropyltrimethoxysilane (GPTMS), and Triton X-100. The developed sensor demonstrates high mechanical strength and flexibility. The PDMS encapsulation improves the sensitivity, response time, and makes the sensor more resilient against both cyclic and static bending deformation. The encapsulated sensor has a sensitivity of 0.83 %/°C with a fast response time of 19 sec. and a recovery time of 38 s against the hotplate surface (ceramic) and it shows improved response time of ∼5.8 s when tested on human skin. Further, PDMS encapsulation enables the sensor to withstand a bending radius as small as 0.15 cm for tensile bending and up to 0.2 cm for compressive bending.
{"title":"Elastomeric encapsulation assisted stability enhancement of polymeric temperature sensor","authors":"Kamalesh Tripathy, Mitradip Bhattacharjee","doi":"10.1016/j.sna.2026.117462","DOIUrl":"10.1016/j.sna.2026.117462","url":null,"abstract":"<div><div>A highly sensitive, stable, and flexible temperature sensor is in high demand for numerous applications such as robotics, e-skin, healthcare, etc. Flexible sensors are prone to high mechanical stress during the fabrication process as well as during operation. Sensor packaging with proper encapsulation prevents unwanted damage to the sensor, increasing its longevity. Keeping this in mind, we fabricated a flexible polydimethylsiloxane (PDMS) encapsulated temperature sensor on a PET (polyethylene terephthalate) for human body temperature measurement. The active layer for the sensor is a composite of Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), graphene oxide (GO), 3-Glycidyloxypropyltrimethoxysilane (GPTMS), and Triton X-100. The developed sensor demonstrates high mechanical strength and flexibility. The PDMS encapsulation improves the sensitivity, response time, and makes the sensor more resilient against both cyclic and static bending deformation. The encapsulated sensor has a sensitivity of 0.83 %/°C with a fast response time of 19 sec. and a recovery time of 38 s against the hotplate surface (ceramic) and it shows improved response time of ∼5.8 s when tested on human skin. Further, PDMS encapsulation enables the sensor to withstand a bending radius as small as 0.15 cm for tensile bending and up to 0.2 cm for compressive bending.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"400 ","pages":"Article 117462"},"PeriodicalIF":4.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145969156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-06DOI: 10.1016/j.sna.2025.117433
Jingwen Gao , Bingcong Leng , Siyuan Xing , Lin Zhang , Jianping Li , Hailong Tian
Currently, there are four different types of stepping piezoelectric actuators: ultrasonic, inchworm, stick-slip and impact inertia. In this work, a novel piezoelectric actuator is proposed: peristaltic piezoelectric actuator, which fundamentally differs from existing piezoelectric actuator driving modes. The peristaltic piezoelectric actuator imitates the movement of earthworms and uses three sets of modified triangular wave drive flexible mechanisms with a phase difference of 120° and a symmetry of 66.7 %. Thus, the slider of peristaltic piezoelectric actuator is consistently subjected to a positive driving force. The actuator proposed in this work is driving by piezoelectric shear stacks, which outputs tangential displacement while bearing axial load. It facilitates the miniaturization of the actuator. Furthermore, a dynamic model of a peristaltic piezoelectric driver based on piezoelectric shear stacking was developed and simulated by MATLAB/Simulink. Experimental results show that the proposed peristaltic piezoelectric actuator can achieve no displacement retreat at f = 5 Hz and stable motion at f > 20 Hz. The proposed actuator has a highly consistent forward and reverse driving performance. The peristaltic piezoelectric actuator based on piezoelectric shear stacks is small in size, simple in structure, and high in the consistency of bidirectional driving performance, which can effectively achieve smooth motion and reduce the vibration and noise of the actuator. The novel driving principle of the proposed peristaltic piezoelectric actuator holds significant potential for advancing piezoelectric actuator technology and merits further investigation.
{"title":"Peristaltic piezoelectric actuator: A new type of piezoelectric actuator that imitate the movement of earthworms","authors":"Jingwen Gao , Bingcong Leng , Siyuan Xing , Lin Zhang , Jianping Li , Hailong Tian","doi":"10.1016/j.sna.2025.117433","DOIUrl":"10.1016/j.sna.2025.117433","url":null,"abstract":"<div><div>Currently, there are four different types of stepping piezoelectric actuators: ultrasonic, inchworm, stick-slip and impact inertia. In this work, a novel piezoelectric actuator is proposed: peristaltic piezoelectric actuator, which fundamentally differs from existing piezoelectric actuator driving modes. The peristaltic piezoelectric actuator imitates the movement of earthworms and uses three sets of modified triangular wave drive flexible mechanisms with a phase difference of 120° and a symmetry of 66.7 %. Thus, the slider of peristaltic piezoelectric actuator is consistently subjected to a positive driving force. The actuator proposed in this work is driving by piezoelectric shear stacks, which outputs tangential displacement while bearing axial load. It facilitates the miniaturization of the actuator. Furthermore, a dynamic model of a peristaltic piezoelectric driver based on piezoelectric shear stacking was developed and simulated by MATLAB/Simulink. Experimental results show that the proposed peristaltic piezoelectric actuator can achieve no displacement retreat at <em>f</em> = 5 Hz and stable motion at <em>f</em> > 20 Hz. The proposed actuator has a highly consistent forward and reverse driving performance. The peristaltic piezoelectric actuator based on piezoelectric shear stacks is small in size, simple in structure, and high in the consistency of bidirectional driving performance, which can effectively achieve smooth motion and reduce the vibration and noise of the actuator. The novel driving principle of the proposed peristaltic piezoelectric actuator holds significant potential for advancing piezoelectric actuator technology and merits further investigation.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117433"},"PeriodicalIF":4.9,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report, to the best of our knowledge, the first demonstration of gas-responsive, self-healing core-sheath fibers fabricated via coaxial electrospinning of polymer cholesteric liquid crystals (PCLCs) with a UV-polymerized cholesteric core encapsulated within a polyvinylpyrrolidone (PVP) sheath. Whereas conventional electronic VOC sensors lack molecular selectivity and most liquid-crystal-based photonic sensors suffer from slow and irreversible response due to the fluidic nature of the mesogens, in-situ photopolymerization under low-intensity UV irradiation (1.0 mW/cm2) permanently stabilizes the helical superstructure inside highly porous fibers (diameter 2.5–4.5 μm). The resulting membranes exhibit excellent vapor permeability, enabling rapid multidirectional VOC diffusion. Upon exposure to acetone and butanone vapors (25–200 μL) in a 20.25 cm3 semi-open chamber, the fibers exhibit distinct, ultrafast (<5 s for 200 μL acetone) and fully reversible optical transitions from bright selective Bragg reflection to an isotropic dark state under polarized optical microscopy. Quantitative grayscale analysis confirms a reliable detection threshold of 25 μL (∼4.08 × 105 ppm acetone, ∼3.37 × 105 ppm butanone) and complete recovery within ∼5 s after vapor removal. Higher UV-curing intensity further accelerates response kinetics by increasing network porosity. This PCLC core-sheath platform uniquely combines mechanical robustness, self-healing capability, high optical sensitivity, rapid reversibility, and long-term reusability without external power, offering a scalable, flexible, label-free, low-power photonic alternative to conventional LC films and electronic gas sensors for real-time environmental, industrial, and biomedical VOC detection.
{"title":"Gas-responsive cholesteric core-sheath fibers with UV-stabilized helical order for ultrafast and reversible VOC sensing","authors":"Ping-Hsueh Chiang, Bhupendra Pratap Singh, Shug-June Hwang","doi":"10.1016/j.sna.2026.117461","DOIUrl":"10.1016/j.sna.2026.117461","url":null,"abstract":"<div><div>We report, to the best of our knowledge, the first demonstration of gas-responsive, self-healing core-sheath fibers fabricated via coaxial electrospinning of polymer cholesteric liquid crystals (PCLCs) with a UV-polymerized cholesteric core encapsulated within a polyvinylpyrrolidone (PVP) sheath. Whereas conventional electronic VOC sensors lack molecular selectivity and most liquid-crystal-based photonic sensors suffer from slow and irreversible response due to the fluidic nature of the mesogens, in-situ photopolymerization under low-intensity UV irradiation (1.0 mW/cm<sup>2</sup>) permanently stabilizes the helical superstructure inside highly porous fibers (diameter 2.5–4.5 μm). The resulting membranes exhibit excellent vapor permeability, enabling rapid multidirectional VOC diffusion. Upon exposure to acetone and butanone vapors (25–200 μL) in a 20.25 cm<sup>3</sup> semi-open chamber, the fibers exhibit distinct, ultrafast (<5 s for 200 μL acetone) and fully reversible optical transitions from bright selective Bragg reflection to an isotropic dark state under polarized optical microscopy. Quantitative grayscale analysis confirms a reliable detection threshold of 25 μL (∼4.08 × 10<sup>5</sup> ppm acetone, ∼3.37 × 10<sup>5</sup> ppm butanone) and complete recovery within ∼5 s after vapor removal. Higher UV-curing intensity further accelerates response kinetics by increasing network porosity. This PCLC core-sheath platform uniquely combines mechanical robustness, self-healing capability, high optical sensitivity, rapid reversibility, and long-term reusability without external power, offering a scalable, flexible, label-free, low-power photonic alternative to conventional LC films and electronic gas sensors for real-time environmental, industrial, and biomedical VOC detection.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117461"},"PeriodicalIF":4.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.sna.2026.117459
Guoxin Yang, Chuanbiao Liu, Yuan Chen, Lei Han, Qing-An Huang
Hydroplaning induced by standing water seriously impacts driving safety. Therefore, real-time, cost-effective in situ measurements of water film thickness on road pavement are critical for early warning. Microwave propagation through a water film results in a measurable phase change, by which the thickness is accurately determined. However, water salinity variations on actual road pavements induce phase and amplitude shifts in microwaves, thereby significantly degrading the measurement accuracy. To mitigate the limitations of current methods, a salinity-compensation equivalent impedance model for measuring water film thickness is proposed. This model analytically determines the amplitude and phase shifts of microwave reflection signals induced by salinity variations. Based on this theoretical model, a water film thickness measurement system integrating a microstrip antenna and a conductivity detection module is designed. In parallel, the antenna, microwave detector, four-port power divider circuit, and reconfigurable phase circuit are integrated on a single printed circuit board (PCB) via a back-feed method. Both experiments and simulations verify the proposed model. Through the compensation of hardware and algorithms based on the salinity-compensation equivalent impedance, high-precision, low-cost in-situ measurements have been achieved. The fabricated system can accurately measure water film thicknesses up to 7 mm at a frequency of 2.4 GHz. Notably, after salinity compensation, the maximum error is reduced to 0.302 mm, accompanied by a minimum accuracy improvement of 54.96 %.
{"title":"Analysis and compensation of microwave amplitude-phase shift induced by water salinity in water film thickness measurement on road pavement","authors":"Guoxin Yang, Chuanbiao Liu, Yuan Chen, Lei Han, Qing-An Huang","doi":"10.1016/j.sna.2026.117459","DOIUrl":"10.1016/j.sna.2026.117459","url":null,"abstract":"<div><div>Hydroplaning induced by standing water seriously impacts driving safety. Therefore, real-time, cost-effective in situ measurements of water film thickness on road pavement are critical for early warning. Microwave propagation through a water film results in a measurable phase change, by which the thickness is accurately determined. However, water salinity variations on actual road pavements induce phase and amplitude shifts in microwaves, thereby significantly degrading the measurement accuracy. To mitigate the limitations of current methods, a salinity-compensation equivalent impedance model for measuring water film thickness is proposed. This model analytically determines the amplitude and phase shifts of microwave reflection signals induced by salinity variations. Based on this theoretical model, a water film thickness measurement system integrating a microstrip antenna and a conductivity detection module is designed. In parallel, the antenna, microwave detector, four-port power divider circuit, and reconfigurable phase circuit are integrated on a single printed circuit board (PCB) via a back-feed method. Both experiments and simulations verify the proposed model. Through the compensation of hardware and algorithms based on the salinity-compensation equivalent impedance, high-precision, low-cost in-situ measurements have been achieved. The fabricated system can accurately measure water film thicknesses up to 7 mm at a frequency of 2.4 GHz. Notably, after salinity compensation, the maximum error is reduced to 0.302 mm, accompanied by a minimum accuracy improvement of 54.96 %.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117459"},"PeriodicalIF":4.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.sna.2026.117460
Rajat Subhra Karmakar , Hsin-Fu Lin , Chia-Ching Huang , Jhih-Fong Huang , Jui-I Chao , Chun-Hway Hsueh , Ying-Chih Liao , Yen-Wen Lu
Instability of electrical contact resistance (ECR) remains a major barrier to the reliability of resistive tactile sensors. This study introduces a materials-driven strategy that embeds silver-coated copper (Ag-Cu) microparticles in a polyethylene glycol (PEG) matrix to stabilise interfacial contacts under mechanical loading. The Ag-Cu fillers form conductive bridges and interfacial interlocking within the composite, directly addressing the drift and hysteresis that typically limit ECR-based devices. A pentagon-knot origami structure was employed to amplify pressure response, yielding a peak sensitivity of 7.3 kPa⁻¹ at 0.05 kPa with 10 wt% Ag-Cu loading. Long-term cycling confirmed stability, and integration into a physiotherapeutic foam roller demonstrated applicability for real-time monitoring of muscle pressure during exercise. These results establish ECR stabilisation through particle–matrix interface engineering as a scalable route toward robust and sensitive pressure sensor for wearable and human-interactive systems.
{"title":"Stabilizing electrical contact resistance in flexible tactile sensors using Ag-Cu/PEG hybrid composites","authors":"Rajat Subhra Karmakar , Hsin-Fu Lin , Chia-Ching Huang , Jhih-Fong Huang , Jui-I Chao , Chun-Hway Hsueh , Ying-Chih Liao , Yen-Wen Lu","doi":"10.1016/j.sna.2026.117460","DOIUrl":"10.1016/j.sna.2026.117460","url":null,"abstract":"<div><div>Instability of electrical contact resistance (ECR) remains a major barrier to the reliability of resistive tactile sensors. This study introduces a materials-driven strategy that embeds silver-coated copper (Ag-Cu) microparticles in a polyethylene glycol (PEG) matrix to stabilise interfacial contacts under mechanical loading. The Ag-Cu fillers form conductive bridges and interfacial interlocking within the composite, directly addressing the drift and hysteresis that typically limit ECR-based devices. A pentagon-knot origami structure was employed to amplify pressure response, yielding a peak sensitivity of 7.3 kPa⁻¹ at 0.05 kPa with 10 wt% Ag-Cu loading. Long-term cycling confirmed stability, and integration into a physiotherapeutic foam roller demonstrated applicability for real-time monitoring of muscle pressure during exercise. These results establish ECR stabilisation through particle–matrix interface engineering as a scalable route toward robust and sensitive pressure sensor for wearable and human-interactive systems.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117460"},"PeriodicalIF":4.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.sna.2026.117463
Joost Wijnmaalen, Leon Abelmann, Iulian Apachitei
This study compares the propulsion of scaled-up helical microrobot models, based on hard- and soft-magnetic elements under rotating magnetic fields. The experiments were performed at the millimeter scale and interpreted using hydrodynamic scaling laws to predict microscale behavior. Results show that hard-magnetic microrobots achieved step-out frequencies and maximum propulsion speeds 4.5 times higher than soft-magnetic microrobots. Below saturation magnetization, soft-magnetic microrobots demonstrated similar performance irrespective of magnetic susceptibility, highlighting that torque generation in these materials is purely geometry-dependent. Employing a tapered ribbon design increased propulsion speed by a factor of 3.5 compared to regular helical designs. These results show that the impact of using soft rather than hard magnets is manageable, allowing for biodegradable magnets such as pure iron. The theory and experiments in this paper provide a quantitative basis for selecting materials and designs.
{"title":"Comparison of the propulsion of helical robots moving at low reynolds numbers based on hard- and soft-magnetic elements","authors":"Joost Wijnmaalen, Leon Abelmann, Iulian Apachitei","doi":"10.1016/j.sna.2026.117463","DOIUrl":"10.1016/j.sna.2026.117463","url":null,"abstract":"<div><div>This study compares the propulsion of scaled-up helical microrobot models, based on hard- and soft-magnetic elements under rotating magnetic fields. The experiments were performed at the millimeter scale and interpreted using hydrodynamic scaling laws to predict microscale behavior. Results show that hard-magnetic microrobots achieved step-out frequencies and maximum propulsion speeds 4.5 times higher than soft-magnetic microrobots. Below saturation magnetization, soft-magnetic microrobots demonstrated similar performance irrespective of magnetic susceptibility, highlighting that torque generation in these materials is purely geometry-dependent. Employing a tapered ribbon design increased propulsion speed by a factor of 3.5 compared to regular helical designs. These results show that the impact of using soft rather than hard magnets is manageable, allowing for biodegradable magnets such as pure iron. The theory and experiments in this paper provide a quantitative basis for selecting materials and designs.</div></div>","PeriodicalId":21689,"journal":{"name":"Sensors and Actuators A-physical","volume":"399 ","pages":"Article 117463"},"PeriodicalIF":4.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.sna.2026.117451
Zhaoling Huang , Hao Zhou , Zhiyan Guo , Qian Ma , Chengqi Ge , Yubing Gong , Md Eshrat E. Alahi , Qi Zeng
Flexible capacitive pressure sensors (CPS) have emerged as transformative components in next-generation wearable electronics, demonstrating unparalleled performance in precision health monitoring, human-robot interaction interfaces, and industrial Internet of Things (IoT) applications due to their unique performance advantages. Compared with traditional resistive or piezoresistive sensing alternatives, capacitive pressure sensors exhibit superior energy efficiency, enhanced pressure sensitivity, and extended dynamic linear response ranges, driven by optimized dielectric layer architectures and advanced stress distribution modulation mechanisms. These have been achieved through modular sensor platforms through the tailoring of dielectric composites, implementation of gradient dielectric architectures, and innovation in contactless charge-transfer protocols, enabling scalable deployment across diverse biomedical and industrial applications. This review will systematically discuss the recent advancements in flexible CPS from the aspects of dielectric layer materials, the structural design of dielectric layer, and the electrode layer architecture. Emphasis will be placed on the challenges and innovative approaches to enhance sensitivity, expand linear working range, and reduce response time, while cutting-edge research directions such as artificial intelligence (AI)-assisted design and reliability evaluation systems, and their major application areas will be analyzed in depth. Finally, the current technological bottlenecks and future development trends will also be discussed prospectively.
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