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We present a novel diagnostic system, based on the principle of capacitive sensing, capable of detecting the conduction zone of detonating explosives. The method relies on measuring the change in the capacitive coupling between a printed circuit and its surroundings, induced by an increase in local conductivity. A high frequency wave generator provides the driving signal, which is modified by the change in coupling. This method boasts greater sensitivity than existing conductivity-based techniques, with comparable spatial and temporal resolution. The subject material was pentaerythritol tetranitrate (PETN) powder, pressed into low density (50%–85% theoretical maximum density) cylindrical columns. Previous attempts to measure the reaction zone of low density PETN have faced difficulties because of its short length and low conductivity compared to other explosives. The PETN was initiated using a laser flyer detonator in order to reach detonation promptly and with a minimum of electrical noise. Application of the capacitive sensor diagnostic and subsequent analysis yielded a density dependent steady-state reaction zone length of between 45 and 78 μ m. [ABSTRACT FROM AUTHOR]

Cooperative robots that perform safety functions as part of cooperative work with humans have been recently drawing attention. Proximity and tactile sensors that can be retrofitted to a robot's surface are important safety measures for existing robots that are not manufactured as cooperative robots to be used as cooperative robots. In this paper, a string‐like self‐capacitance‐based proximity and tactile sensor that can be easily wrapped around various types of existing robots is proposed. The novel and useful point in this paper is that it can be easily mounted on various robots by a flexible string‐like proximity and tactile sensor. The sensor module can be adjusted to the required length by connecting different numbers of modules depending on the mounting surface. As a demonstration, six prototype sensor modules were connected by each connector and wrapped around a robotic arm. The sensor modules on the robot's surface could detect an object within its proximity range and detect the rough pressure after contact. In addition, the robotic arm with the sensor modules could be controlled in real time using the data obtained from the sensor that are object detection data at proximity range. These results confirm that the proposed sensor module can be used in the proximity and tactile sensors of existing robots. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) elastomer composites offer promising potential in soft robotics, wearable electronics, and human‐machine interfaces. Direct ink write (DIW) 3D printing offers a versatile manufacturing technique capable of precise control over LM microstructures, yet challenges such as interfilament void formation in multilayer structures impact material performance. Here, a DIW strategy is introduced to control both LM microstructure and material architecture. Investigating three key process parameters–nozzle height, extrusion rate, and nondimensionalized nozzle velocity–it is found that nozzle height and velocity predominantly influence filament geometry. The nozzle height primarily dictates the aspect ratio of the filament and the formation of voids. A threshold print height based on filament geometry is identified; below the height, significant surface roughness occurs, and above the ink fractures, which facilitates the creation of porous structures with tunable stiffness and programmable LM microstructure. These porous architectures exhibit reduced density and enhanced thermal conductivity compared to cast samples. When used as a dielectric in a soft capacitive sensor, they display high sensitivity (gauge factor = 9.0), as permittivity increases with compressive strain. These results demonstrate the capability to simultaneously manipulate LM microstructure and geometric architecture in LM elastomer composites through precise control of print parameters, while maintaining geometric fidelity in the printed design. [ABSTRACT FROM AUTHOR]

Limited or absent haptic feedback is reported as a factor hindering the continued adoption of surgical robots. This article presents a proof of concept for vibrotactile feedback integrated into a continuum robot to explore whether such feedback improves spatial perception in surgical settings. The robot is equipped with a capacitive sensor for noncontact endoscope localization, enabling spatial awareness of the robot's tool center point (TCP) within the surgical environment. The data from the sensor is processed and transmitted to a bracelet worn by the user, which generates vibrotactile feedback. The bracelet contains four vibration motors providing tactile cues for navigation and positioning of the robot's TCP. All subsystems are integrated into a unified system to deliver vibrotactile feedback to the user. When the user maneuvers the TCP of the robot near an object, they receive vibrotactile feedback via the bracelet. Thereby, the intensity of vibration increases as the TCP approaches the object, and the direction of the obstacle is mapped on the bracelet. Initial functional tests were performed and prove the functionality of the proposed system. [ABSTRACT FROM AUTHOR]

Process microminiaturization is in need not only in chip field, but also in sensor‐related industries. Touch panel sensors as an example have their man‐machine interactive performance in high relation with the circuit resolution. Traditional etchings by yellow light or laser encounter their resolution limit of ≈50 µm; moreover, former pollution using chemical etchants and latter damage to flexible substrates are inevitable. This paper demonstrates an efficient and green patterning technology for flexible silver nanowire (AgNW) transparent and conductive films, which can enable complicated patterns on various types of substrates with high resolution of a 30 µm line width and 40 µm line spacing. The approach uses a water‐soluble photosensitive polymer as the selective protection layer to facilitate the removal of unwanted AgNWs through simple water washing. Due to its good water resistance and mechanical properties, the patterned electrodes exhibit excellent flexibility and environmental stability. As a proof of concept, a capacitive proximity sensor is designed using the patterned AgNW electrodes of the micro feature size, which exhibits excellent proximity sensing performance. The developed patterning technology paves the way to miniaturized feature sizes of different optoelectronic devices for wide applications in fields like new‐style displays, man‐machine interaction, IoT sensing and intelligent robots. [ABSTRACT FROM AUTHOR]

Silk nanofibers (SNFs) from abundant sources are low‐cost and environmentally friendly. Combined with other functional materials, SNFs can help create bioelectronics with excellent biocompatibility without environmental concerns. However, it is still challenging to construct an SNF‐based composite with high conductivity, flexibility, and mechanical strength for all SNF‐based electronics. Herein, this work reports the design and fabrication of Ti3C2Tx‐silver@silk nanofibers (Ti3C2Tx‐Ag@SNF) composites with multi‐dimensional heterogeneous conductive networks using combined in situ growth and vacuum filtration methods. The ultrahigh electrical conductivity of Ti3C2Tx‐Ag@SNF composites (142959 S m−1) provides the kirigami‐patterned soft heaters with a rapid heating rate of 87 °C s−1. The multi‐dimensional heterogeneous network further allows the creation of electromagnetic interference shielding devices with an exceptionally high specific shielding effectiveness of 10,088 dB cm−1. Besides working as a triboelectric layer to harvest the mechanical energy and recognize the hand gesture, the Ti3C2Tx‐Ag@SNF composites can also be combined with an ionic layer to result in a capacitive pressure sensor with a high sensitivity of 410 kPa−1 in a large range due to electronic‐double layer effect. The applications of the Ti3C2Tx‐Ag@SNF composites in recognizing human gestures and human‐machine interfaces to wirelessly control a trolley demonstrate the future development of all SNF‐based electronics. [ABSTRACT FROM AUTHOR]

Multimodal tactile sensors, as key information input channel in human‐machine interactions, have faced the significant challenges including high power‐consumption, multimodal data fusion, and wireless transmission. In this work, a battery‐free multimodal wireless tactile sensor (TC‐MWTS) based on tribo‐capacitive coupled effect for normal and shear force fusion sensing is proposed, which is enabled by a 3D structure combining a triboelectric sensor and a capacitive sensor coupled with an inductive coil. A triboelectric sensor equipped with contact‐discharge structures exhibits 25‐fold wireless signal enhancement compared to conventional triboelectric sensors. Based on the characteristics of dual time‐frequency domain information existing in the wireless signals, both normal and shear forces can simultaneously be converted into voltage amplitude V and eigenfrequency f, respectively, without crosstalk and complex decoupling signals. The TC‐MWTS exhibits a maximum sensitivity of 2.47 V kPa−1 for normal force from 2 to 30 kPa and a sensitivity of 0.28 MHz N−1 for shear force between 0.3 and 1.0 N. Finally, the excellent sensing capability of TC‐MWTS to sense complex multidimensional forces in human‐machine interaction is demonstrated. This work innovatively proposes a new mechanism and methodology for effectively fusing and processing multimodal tactile information, which may drive the tremendous development of low‐power multimodal tactile sensing system. [ABSTRACT FROM AUTHOR]

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Proximity sensing technology, which can obtain information without physical contact, has become an ideal choice in scenarios where physical contact is not feasible. Despite substantial advancements in tactile sensing, proximity sensing technology still holds great potential and has yet to be fully developed. Among numerous proximity sensing technologies, the fringing‐effect‐based capacitive proximity sensor (FE‐CPS) has garnered considerable attention due to its low cost, low power consumption, wide sensing range, and flexible and versatile structural design. However, research on FE‐CPS has not yet formed a complete system, and its development and intellectualization are still in their infancy, urgently requiring a systematic review to advance its development. This paper systematically summarizes the recent advances in FE‐CPS, from basic theory to practical applications. The working principle and typical structure of FE‐CPS are first introduced, followed by a discussion of methods for optimizing device performance. Furthermore, the application scenarios of FE‐CPS in intelligent pre‐alarm systems, intelligent control systems, and intelligent material perception systems are reviewed. Finally, the future development and challenges faced by FE‐CPS are prospected. [ABSTRACT FROM AUTHOR]

Smart contact lenses (SCLs), integrating various functional components, serve as a platform for wirelessly intraocular pressure (IOP) monitoring. Accurate and dynamic measurements offer crucial clinical references for patients with ocular hypertension. Nevertheless, the complex ocular environment poses great challenges, particularly for inductor–capacitor–resistor (LCR) type IOP sensors, which suffer signal instability due to variations of ocular dielectric properties. Here, an innovative IOP monitoring sensor with robust environmental stability, achieved by integrating the ground shield, is proposed. Employing a capacitive pressure sensor with porous polydimethylsiloxane (PDMS) structure encased in a hydrogel, the study successfully demonstrates high‐sensitivity monitoring of IOP changes using in vitro porcine eyes. This optimized design empowers the wireless IOP sensor with a sensitivity of 1.15 ‰/mmHg. It exhibits exceptional frequency stability after undergoing 100 wear cycles on ten distinct porcine eyes and remains reliable across a wide range of metabolite concentrations typical of normal eyes. Notably, any observed frequency shift translates into IOP changes within a 3 mmHg range, showcasing its suitability for repeated use and daily IOP monitoring. [ABSTRACT FROM AUTHOR]

A circular non-touch mode capacitive pressure sensor can operate in both transverse and normal uniform loading modes, but the elastic behavior of its movable electrode plate is different under the two different loading modes, making its input–output analytical relationships between pressure and capacitance different. This suggests that when such a sensor operates, respectively, in transverse and normal uniform loading modes, the theory of its numerical design and calibration is different, in other words, the theory for the transverse uniform loading mode (available in the literature) cannot be used as the theory for the normal uniform loading mode (not yet available in the literature). In this paper, a circular non-touch mode capacitive pressure sensor operating in normal uniform loading mode is considered. The elastic behavior of the movable electrode plate of the sensor under normal uniform loading is analytically solved with the improved governing equations, and the improved analytical solution obtained can be used to mathematically describe the movable electrode plate with larger elastic deflections, in comparison with the existing two analytical solutions in the literature. This provides a larger technical space for developing the circular non-touch mode capacitive pressure sensors used for measuring the static gas pressure (belonging to normal uniform loading). [ABSTRACT FROM AUTHOR]

Flexible, wearable pressure sensors offer numerous benefits, including superior sensing capabilities, a lightweight and compact design, and exceptional conformal properties, making them highly sought after in various applications including medical monitoring, human–computer interactions, and electronic skins. Because of their excellent characteristics, such as simple fabrication, low power consumption, and short response time, capacitive pressure sensors have received widespread attention. As a flexible polymer material, polydimethylsiloxane (PDMS) is widely used in the preparation of dielectric layers for capacitive pressure sensors. The Young's modulus of the flexible polymer can be effectively decreased through the synergistic application of sacrificial template and laser ablation techniques, thereby improving the functionality of capacitive pressure sensors. In this study, a novel sensor was introduced. Its dielectric layer was developed through a series of processes, including the use of a sacrificial template method using NaCl microparticles and subsequent CO2 laser ablation. This porous PDMS dielectric layer, featuring an array of holes, was then sandwiched between two flexible electrodes to create a capacitive pressure sensor. The sensor demonstrates a sensitivity of 0.694 kPa−1 within the pressure range of 0–1 kPa and can effectively detect pressures ranging from 3 Pa to 200 kPa. The sensor demonstrates stability for up to 500 cycles, with a rapid response time of 96 ms and a recovery time of 118 ms, coupled with a low hysteresis of 6.8%. Furthermore, our testing indicates that the sensor possesses limitless potential for use in detecting human physiological activities and delivering signals. [ABSTRACT FROM AUTHOR]

The fabrication of flexible electronics has gained extensive attention due to the growing demand of flexible devices. Among various methods, laser direct writing technology has emerged as a promising approach due to its advantages of high processing accuracy and simplicity. This research focuses on the preparation of copper microelectrodes using laser‐induced reduction of CuO nanoparticles (Cu NPs) on polyethylene terephthalate films. First, the influence of various parameters on the conductivity of the copper microelectrodes is investigated. Second, flexible copper microelectrodes with a minimum resistivity of 62.29 μΩ cm and an adhesion grade of 4B level are successfully fabricated. Building upon these results, a capacitive pressure sensor is developed with optimal sensitivity of 3.99 Pa−1, good hysteresis of 3.99%, and response and recovery times of 1.2 and 1.3 s, respectively. Repeatability tests confirm the sensor's stability and fatigue resistance. This research provides valuable insights for the production of flexible sensors. [ABSTRACT FROM AUTHOR]

Schematic illustration of plantar pressure distribution visualization system including a 9-channel pressure sensor array, analog to digital converter, data analysis software, and operation interface. [Display omitted] Based on real-time detection of plantar pressure, gait recognition could provide important health information for rehabilitation administration, fatigue prevention, and sports training assessment. So far, such researches are extremely limited due to lacking of reliable, stable and comfortable plantar pressure sensors. Herein, a strategy for preparing high compression strength and resilience conductive iongels has been proposed by implanting physically entangled polymer chains with covalently cross-linked networks. The resulting iongels have excellent mechanical properties including nice compliance (young's modulus < 300 kPa), high compression strength (>10 MPa at a strain of 90 %), and good resilience (self-recovery within seconds). And capacitive pressure sensor composed by them possesses excellent sensitivity, good linear response even under very small stress (∼kPa), and long-term durability (cycles > 100,000) under high-stress conditions (133 kPa). Then, capacitive pressure sensor arrays have been prepared for high-precision detection of plantar pressure spatial distribution, which also exhibit excellent sensing performances and long-term stability. Further, an extremely sensitive and fast response plantar pressure monitoring system has been designed for monitoring plantar pressure of foot at different postures including upright, forward and backward. The system achieves real-time tracking and monitoring of changes of plantar pressure during different static and dynamic posture processes. And the characteristics of plantar pressure information can be digitally and photography displayed. Finally, we propose an intelligent framework for real-time detection of plantar pressure by combining electronic insoles with data analysis system, which presents excellent applications in sport trainings and safety precautions. [ABSTRACT FROM AUTHOR]

This study introduces a novel wearable device that combines dual‐functional modules for energy storage and sensing. The device features an ionic gel serving as both the battery electrolyte and sensor dielectric layer, along with VO2‐nanoneedles electrodes. The solid‐state zinc‐ion battery module demonstrates a specific capacity of 286 mAh g−1, delivering consistent and long‐lasting power output even under variable pressure conditions. Moreover, the iontronic pressure sensor module exhibits high sensitivity, achieving 2.3 × 104 kPa−1, enabling precise detection of fingertip pulses and identification of respiratory patterns. The device's flexibility and structural resilience allow it to endure complex deformations, ensuring continuous operation in challenging environments. These results highlight the potential of the all‐in‐one device for wearable smart healthcare monitoring and management. [ABSTRACT FROM AUTHOR]

In contrast to conventional non-destructive testing (NDT) and non-destructive evaluation (NDE) methodologies, including radiography, ultrasound, and eddy current analysis, coplanar capacitive sensing technique emerges as a novel and promising avenue within the field. This paper endeavors to elucidate the efficacy of coplanar capacitive sensing, also referred to as capacitive imaging (CI), within the realm of NDT. Leveraging extant scholarly discourse, this review offers a comprehensive and methodical examination of the coplanar capacitive technique, encompassing its fundamental principles, factors influencing sensor efficacy, and diverse applications for defect identification across various NDT domains. Furthermore, this review deliberates on extant challenges and anticipates future trajectories for the technique. The manifold advantages inherent to coplanar capacitive sensing vis-à-vis traditional NDT methodologies not only afford its versatility in application but also underscore its potential for pioneering advancements in forthcoming applications. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors are evolving towards higher precision, larger areas, multi-sensing capabilities, increased resolution, and integration, imposing greater demands on the fabrication processes of flexible sensor devices. This study proposes a fully printed fabrication process utilizing electric field-assisted 3D micro-nanojet printing technology to manufacture capacitive sensors. Additionally, it designs sensor simulation studies based on hemispherical structures, cubic structures, and various microstructure arrangement densities to guide the preparation of capacitive pressure sensors. By utilizing PDMS mixed with 10% graphene material to print the dielectric layer with microstructures and conductive silver adhesive to print the electrode layer, the all-printing process significantly enhances the fabrication efficiency of flexible capacitive pressure sensors. The fabricated sensor achieves a maximum sensitivity of 0.7826 kPa−1 with a response time of 90 ms and a recovery time of 50 ms. It exhibits excellent responsiveness and stability during 4000 cycle tests, validating that the flexible capacitive pressure sensor, based on micro-nano-3D printing, can enhance the fabrication efficiency of flexible capacitive sensors and deliver outstanding performance. [ABSTRACT FROM AUTHOR]

The ongoing development of single electron, nano-, and atomic scale semiconductor devices would greatly benefit from a characterization tool capable of detecting single electron charging events with high spatial resolution at low temperatures. In this work, we introduce a novel Atomic Force Microscope (AFM) instrument capable of measuring critical device dimensions, surface roughness, electrical surface potential, and ultimately the energy levels of quantum dots and single electron transistors in ultra miniaturized semiconductor devices. The characterization of nanofabricated devices with this type of instrument presents a challenge: finding the device. We, therefore, also present a process to efficiently find a nanometer sized quantum dot buried in a 10 × 10 mm2 silicon sample using a combination of optical positioning, capacitive sensors, and AFM topography in a vacuum. [ABSTRACT FROM AUTHOR]

Elastomers based on cross‐linked bottlebrush polymers combine an extreme softness at low strains with a strain‐stiffening effect, which makes them attractive as active components in dielectric elastomer actuators (DEA). Their main disadvantage concerns the small relative permittivity, which is about 3.5, requiring relatively high driving voltage in actuators. We synthesized a bottlebrush polymer elastomer with polar brushes, which exhibit an enhanced dielectric permittivity of 4.4. Anionic ring‐opening polymerization of a polar cyclosiloxane gave telechelic polar brushes, while ring‐opening polymerization of a norbornene macromonomer gave a bottlebrush polymer which was cross‐linked to elastomers by a thiol‐ene reaction. Elastomers with a small elastic modulus below 100 kPa, strain at break exceeding 100 %, attractive elasticity, and small mechanical loss factors (tanδ) were achieved. Temperature‐dependent impedance measurements revealed a transition temperature of −95 °C and an interfacial polarization. The multigram scale synthesis demonstrates the potential for scaling up, which opens the door to broader applications of these materials beyond actuators, such as capacitive sensors, batteries, and electroluminescent devices. Notably, these devices operate at extremely low voltages where the dielectric breakdown does not limit their functionality, but still, the softness and the increased dielectric permittivity are a plus. [ABSTRACT FROM AUTHOR]

Conductive hydrogels have been promising candidates for wearable and flexible electronics due to their high flexibility and biocompatibility. However, the previously reported hydrogels with conductivity over 1000 S m−1 usually have poor mechanical properties including low tensile stress (<5 MPa) and toughness (<2 MJ m−3). Here, a liquid metal‐doped polyvinyl alcohol (PVA‐LM) hydrogel is presented, which simultaneously combines ultra‐high conductivity (maximum of 217 895 S m−1) with excellent mechanical properties, including high tensile stress (15.44 MPa), large tensile strain (704%), high toughness (43.02 MJ m−3) and excellent fatigue resistance. Such extremely high conductivity is afforded by self‐sintering behavior of LM at the bottom surface that enables the formation of conductive networks. The formation of polymer crystalline regions and polymer‐tannic acid multiple hydrogen bonds are responsible for the impressive mechanical properties of conductive hydrogels. Particularly, the electric LM filler could be recycled in the robust hydrogel by dissociation of multiple dynamic interactions. Most importantly, wearable electrodes and capacitive sensors are developed utilizing PVA‐LM hydrogel. These devices enable accurate monitoring of bioelectrical signals and human motions, highlighting their immense potential in the realm of soft electronics and wearable technology. [ABSTRACT FROM AUTHOR]

Strong chemical or voltage‐driven studies of gallium alloys (liquid metal, LM) show methods of altering the surface energy of the bare alloys by controlling Ga2O3 (Gallium Oxide)‐ a 3‐5 nm surface oxide that forms on LM. However, various fluids (i.e., water) interact weakly compared to strong acids or bases and do not etch Ga2O3. Specialized instruments are often required to study such interactions, which are not readily available. Herein, an LM‐based nanoporous conductive wire platform is demonstrated, which can effectively be utilized for real‐time weaker interfacial studies. The unconventional platform allows fluid transport and interfacial studies within the nanoporous domain, which is still foreign in the literature. Nanoporous conductive wires are fabricated by injecting eutectic gallium indium (eGaIn) into hollow microtubes collected from expired and unused artificial kidneys. These steps upcycle medical waste and confine Ga2O3 at the nanopores for an inexpensive metal‐oxide/metal framework. The platform for interfacial fluidics is harnessed, leveraging deionized (DI) water, 1 m hydrochloric acid (HCl), and 95% ethanol (EtOH). This study also demonstrates capacitive sensors that can be immediately implemented using nanoporous conducive wires. Advanced applications from this study suggest that future exploration of such soft systems can lead to more nano/bioanalyses harnessing LM alloys. [ABSTRACT FROM AUTHOR]

A three-axis seismic accelerometer was developed and created, containing three uniaxial mutually perpendicular sensors, the sensitivity axis of each sensor is located at an angle of 54.736° to the local gravitational vertical. For the first time, additional magnetic rigidity has been introduced into each device, allowing the device to be finely tuned to the conditions of a particular planet. However, the accumulated experience in conducting ground-based tests has shown the need to improve the uniaxial seismic accelerometer, which can significantly improve the characteristics of the device. First, we use a single material—beryllium bronze BrB-2—for the manufacture of massive test mass suspension elements with a thickness of 1.5 mm and an elastic element made of a thin strip 10–20 microns thick, which reduces the likelihood of instability. Secondly, we reduce the gap in the capacitors of capacitive converters from 0.25 to 0.1–0.15 mm to significantly increase the conversion slope of the capacitive sensor. Thirdly, we change the technology of setting up the device, for which we combine all the elements of the sensitive part of a uniaxial seismogravimeter using special vertical inserts. This allows us to place the device as a whole in a system for its configuration, eliminating the possibility of failure of individual elements, thereby increasing the reliability of the device. [ABSTRACT FROM AUTHOR]

The design of fast-response, highly sensitive, and eco-friendly sensors for monitoring human psychological and physical activity is an interesting research topic. In this research work, we have designed a semicircular-shaped printed sensor to monitor respiration response. A semicircular-shaped interdigitated elecreodes-based capacitive sensor is designed in CST studio software using its electrostatic physics module and is fabricated using Voltera V1. The substrate material used for the sensor design is flexible PET, and the ink used for electrodes is silver (Ag). The sensor is tested in a humidity chamber, and the response toward humidity is recorded. The sensor response in terms of capacitance is ~ 128 pF at 30%RH and reaches ~ 4400 pF at 100%RH. The response and recovery time of the sensor is 0.87 s and 1.2 s. The sensor is integrated with the medical face mask. The sensor's response to different respiration behaviors is recorded. The sensor shows a repeatable and stable response. The sensor is highly sensitive and is further enhanced for breathing monitoring by connecting another sensor in parallel. The sensor is fast-response, highly sensitive, repeatable, and stable, which makes our fabricated sensor the best fit for multifunctional applications. [ABSTRACT FROM AUTHOR]

Soft pouch motors, engineered to mimic the natural movements of skeletal muscles, play a crucial role in advancing robotics and exoskeleton development. However, the fabrication techniques often involve multistage processes; they lack soft sensing capabilities and are sensitive to cutting and damage. This work introduces a new textile‐based pouch motors with the capacity for biaxial actuation and capacitive sensory functions, achieved through the application of computerized knitting technology using ultrahigh molecular weight polyethylene yarn (Spectra) and conductive silver yarns. This method enables the rapid and scalable mass fabrication of robust pouch motors. The resulting pouch motors exhibit maximum lifting capacity of 10 kg, maximum contraction of 53.3% along the y‐axis, and transverse extension of 41.18% along the x‐axis at 50 kPa pressure. Finite element analysis closely matches the experimental data. The capacitance signals in relation to contraction motion are well suited for detecting air pressure levels and hold promise for applications requiring robotic control. Notably, it effectively elevates an ankle joint simulator at a 20° angle, highlighting its potential for applications such assisting individuals with foot drop. This study presents a practical demonstration of the soft ankle exosuit designed to provide lifting support for individuals facing this mobility challenge. [ABSTRACT FROM AUTHOR]

Ionogels are promising material candidates for ionotronics due to their excellent ionic conductivity, stretchability, and thermal stability. However, it is challenging to develop 3D printable ionogels with both excellent electrical and mechanical properties. Here, we report a highly conductive and stretchable nanostructured (CSN) ionogel for 3D printing ionotronic sensors. We propose the photopolymerization-induced microphase separation strategy to prepare the CSN ionogels comprising continuous conducting nanochannels intertwined with cross-linked polymeric framework. The resultant CSN ionogels simultaneously achieves high ionic conductivity (over 3 S m−1), high stretchability (over 1500%), low degree of hysteresis (0.4% at 50% strain), wide-temperature-range thermostability (−72 to 250 °C). Moreover, its high compatible with DLP 3D printing enables the fabrication of complex ionogel micro-architectures with high resolution (up to 5 μm), which allows us to manufacture capacitive sensors with superior sensing performances. The proposed CSN ionogel paves an efficient way to manufacture the next-generation capacitive sensors with enhanced performance. Achieving high conductivity without sacrificing printability and mechanical properties of ionogels for ionotronics is difficult. Here, the authors report an UV curable ionogel with bicontinuous nanostructures and using dynamic light processing 3D printing, they fabricate high performance ionogel sensors. [ABSTRACT FROM AUTHOR]

In this work, we propose a novel single-end morphing capacitive sensing method for shape tracking, FxC, by combining Folding origami structures and Capacitive sensing to detect the morphing structural motions using state-of-the-art sensing circuits and deep learning. It was observed through embedding areas of origami structures with conductive materials as single-end capacitive sensing patches, that the sensor signals change coherently with the motion of the structure. Different from other origami capacitors where the origami structures are used in adjusting the thickness of the dielectric layer of double-plate capacitors, FxC uses only a single conductive plate per channel, and the origami structure directly changes the geometry of the conductive plate. We examined the operation principle of morphing single-end capacitors through 3D geometry simulation combined with physics theoretical deduction, which deduced similar behavior as observed in experimentation. Then a software pipeline was developed to use the sensor signals to reconstruct the dynamic structural geometry through data-driven deep neural network regression of geometric primitives extracted from vision tracking. We created multiple folding patterns to validate our approach, based on folding patterns including Accordion, Chevron, Sunray and V-Fold patterns with different layouts of capacitive sensors using paper-based and textile-based materials. Experimentation results show that the geometry primitives predicted from the capacitive signals have a strong correlation with the visual ground truth with R-squared value of up to 95% and tracking error of 6.5 mm for patches. The simulation and machine learning constitute two-way information exchange between the sensing signals and structural geometry. By embedding part of the origami surface with morphing single-end capacitive sensors, FxC presents a unique solution that leverages both the mechanical properties of origami and sensing properties of capacitive sensing. [ABSTRACT FROM AUTHOR]

Currently, flexible capacitive sensors have a wide range of application scenarios in the field of wearable electronic devices. In order to detect more subtle joint movements of the human body, a method of fabricating stacked capacitive sensors is demonstrated. An ultrathin dielectric elastomer film of about 110 μm by the "secondary calendering" method was prepared. The shape of the electrode layers was designed, printed the electrode materials on the dielectric elastomer film by screen-printing, realized the stacked-layer technology, and connected each sensor unit in parallel by the electrode columns formed inside. A 12-layer flexible capacitive sensor with an initial capacitance of 10.2nF, good resolution (1% strain), high sensitivity (1.09) and stability under 10,000 cycles is fabricated. The sensor fabricated in this paper can recognize the motion at various joints of the human body, such as elbow and knee joints. This paper provides a new method for fabrication of stacked flexible capacitive sensors, which opens up new applications in flexible sensors, wearable electronic devices and human-computer interaction. [ABSTRACT FROM AUTHOR]

Continuous monitoring of lower extremity muscles is necessary, as the muscles support many human daily activities, such as maintaining balance, standing, walking, running, and jumping. However, conventional electromyography and physiological cross-sectional area methods inherently encounter obstacles when acquiring precise and real-time data pertaining to human bodies, with a notable lack of consideration for user comfort. Benefitting from the fast development of various fabric-based sensors, this paper addresses these current issues by designing an integrated smart compression stocking system, which includes compression garments, fabric-embedded capacitive pressure sensors, an edge control unit, a user mobile application, and cloud backend. The pipeline architecture design and component selection are discussed in detail to illustrate a comprehensive user-centered STIMES design. Twelve healthy young individuals were recruited for clinical experiments to perform maximum voluntary isometric ankle plantarflexion contractions. All data were simultaneously collected through the integrated smart compression stocking system and a muscle force measurement system (Humac NORM, software version HUMAC2015). The obtained correlation coefficients above 0.92 indicated high linear relationships between the muscle torque and the proposed system readout. Two-way ANOVA analysis further stressed that different ankle angles (p = 0.055) had more important effects on the results than different subjects (p = 0.290). Hence, the integrated smart compression stocking system can be used to monitor the muscle force of the lower extremities in isometric mode. [ABSTRACT FROM AUTHOR]

Recycled carbon fibre (rCF) composites are increasingly being explored for applications such as strain sensing, manufacturing of automobile parts, assistive technologies, and structural health monitoring due to their properties and economic and environmental benefits. The high conductivity of carbon and its wide application for sensing makes rCF very attractive for integrating sensing into passive structures. In this paper, capacitive sensors have been fabricated using rCF composites of varying compositions. First, we investigated the suitability of recycled carbon fibre polymer composites for different sensing applications. As a proof of concept, we fabricated five touch/proximity sensors and three soil moisture sensors, using recycled carbon fibre composites and their performances compared. The soil moisture sensors were realised using rCF as electrodes. This makes them corrosion-resistant and more environmental-friendly, compared to conventional soil moisture sensors realised using metallic electrodes. The results of the touch/proximity sensing show an average change in capacitance (ΔC/C~34) for 20 mm and (ΔC/C~5) for 100 mm, distances of a hand from the active sensing region. The results of the soil moisture sensors show a stable and repeatable response, with a high sensitivity of ~116 pF/mL of water in the linear region. These results demonstrate their respective potential for touch/proximity sensing, as well as smart and sustainable agriculture. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing use of digital vibration sensors that are based on capacitive MEMS accelerometers for machine vibration monitoring and diagnostics. These sensors simplify the design of monitoring and diagnostic systems, thus reducing implementation costs. However, it is important to understand how effective these digital sensors are in detecting rolling bearing faults. This article describes a method for determining the diagnostic sensitivity of diagnostic parameters provided by commercially available vibration sensors based on MEMS accelerometers. Experimental tests were conducted in laboratory conditions, during which vibrations from 11 healthy and faulty rolling bearings were measured using two commercial vibration sensors based on MEMS accelerometers and a piezoelectric accelerometer as a reference sensor. The results showed that the diagnostic sensitivity of the parameters depends on the upper-frequency band limit of the sensors, and the parameters most sensitive to the typical fatigue faults of rolling bearings are the peak and peak-to-peak amplitudes of vibration acceleration. Despite having a lower upper-frequency range compared to the piezoelectric accelerometer, the commercial vibration sensors were found to be sensitive to rolling bearing faults and can be successfully used in continuous monitoring and diagnostics systems for machines. [ABSTRACT FROM AUTHOR]

Capacitive humidity sensors typically consist of interdigitated electrodes coated with a dielectric layer sensitive to varying relative humidity levels. Previous studies have investigated different polymeric materials that exhibit changes in conductivity in response to water vapor to design capacitive humidity sensors. However, lipid films like monoolein have not yet been integrated with humidity sensors, nor has the potential use of capacitive sensors for skin hydration measurements been fully explored. This study explores the application of monoolein-coated wireless capacitive sensors for assessing relative humidity and skin hydration, utilizing the sensitive dielectric properties of the monoolein–water system. This sensitivity hinges on the water absorption and release from the surrounding environment. Tested across various humidity levels and temperatures, these novel double functional sensors feature interdigitated electrodes covered with monoolein and show promising potential for wireless detection of skin hydration. The water uptake and rheological behavior of monoolein in response to humidity were evaluated using a quartz crystal microbalance with dissipation monitoring. The findings from these experiments suggest that the capacitance of the system is primarily influenced by the amount of water in the monoolein system, with the lyotropic or physical state of monoolein playing a secondary role. A proof-of-principle demonstration compared the sensor's performance under varying conditions to that of other commercially available skin hydration meters, affirming its effectiveness, reliability, and commercial viability. [ABSTRACT FROM AUTHOR]

Transient electronics with degradability or dissolvability on demand possess remarkable characteristics for wearable, bioelectronic, and implanted electronic devices. While synthetic materials have made significant progress in degradability and stretchability, they suffer from intrinsic limitations, including low degradation rates, poor mechanical compliance, and high production cost, which restrict the growth of transient electronic devices. Herein, a versatile fabrication strategy is presented for transient electronics that combine a resilient biopolymer substrate (gelatin biogels) with liquid metal (Galinstan). The circuits made from gelatin biogel‐based and liquid metal are mechanically resilient and durable, exhibiting good compliance with irregular and deformable surfaces, and thus can withstand long‐term exposure to dynamic deformation (about 60 000 cycles at a strain of 50%). More importantly, gelatin biogels are naturally derived and endowed with thermally reversible gelling, which enables on‐demand rapid dissolution and recycling of the materials. As a proof‐of‐concept, transient circuit‐based capacitive sensors, which can be degraded within 20 s, are fabricated for monitoring finger touching, morse code generation, and electrical touchpad. Such a strategy provides a guideline for designing transient electronics with a combination of biopolymer gels and liquid metal, and this approach is anticipated to find applications in human–machine interfaces and wearable devices. [ABSTRACT FROM AUTHOR]

Flexible capacitive pressure sensors play a crucial role in wearable electronics and robotics. However, their susceptibility to environmental noise poses challenges to sensing precision. To mitigate the impact of environmental influences, a sensor capable of producing signals orders of magnitudes larger than the noise becomes essential. One straightforward method to enhance capacitance values involves reducing the thickness of the dielectric layer. Yet, when this reduction reaches nanometer scale, the dielectric layer may become mechanically vulnerable and more importantly, their charge storage capability is compromised due to electron tunneling. To address these challenges, here the naturally formed alumina (Al2O3) on aluminum (Al) surface is employed as a stable and ultra‐thin dielectric layer. Simultaneously, the Schottky effect at the Al‐Al2O3‐carbon black (CB) interface is harnessed to prevent electron tunneling. These strategies collectively yielded a large unit‐area capacitance (UAC) of 50 nF cm−2 and demonstrated high electrical and environmental stability. Furthermore, hollow hemispherical microstructures are incorporated at the interface, resulting in a flexible pressure sensor with high sensitivity (8.6 kPa−1) and a linear response up to 50 kPa. With its simple two‐layer structure, this sensor can be seamlessly integrated in situ and offers commercial‐grade resolution at mN‐level for monitoring human biomechanical signals. [ABSTRACT FROM AUTHOR]

Due to advancements in Micro-Electro-Mechanical Systems (MEMS) fabrication technologies, researchers are incorporating numerous innovations in the design of capacitive pressure sensors (CPS). This work aims to present a novel CPS design using a plano-convex substrate to enhance the capacitance and sensitivity. Diaphragm deflection occurs due to its elastic property when pressure is applied to the diaphragm. This deflection reduces the distance between the diaphragm and substrate, thereby remarkably increasing capacitance. The Plano-Convex design offers added advantages of increased contact area between the diaphragm and substrate under applied pressure, hence significantly enhancing sensor sensitivity and range. More efficient and miniaturized CPSs are in high demand in medical instrumentation, aerospace, aviation, power plants and automotive industries. This work presents all the required mathematical calculations, modeling and simulations to support the proposed design. The diaphragm deflection simulation concerning pressure is conducted using COMSOL Multiphysics, while MATLAB is employed for analytical simulations related to changes in capacitance and capacitive sensitivity. [ABSTRACT FROM AUTHOR]

A procedure is developed for producing basic electronic components utilizing materials sourced from discarded orange, grapefruit, lemon, apple, banana, potato, and carrot peels. Initially, these materials undergo dehydration, followed by a meticulous pulverization process to obtain fine powder. Natural adhesives like water, honey, sugar, starch, and gelatin are employed to interconnect the materials. Formed substrates are characterized using Scanning Electron Microscopy, Energy Dispersive X‐ray Spectroscopy, and an optical profilometer. Furthermore, the relative permittivity of the materials is determined. Three distinct types of substrates, derived from the aforementioned peels, are crafted in varying dimensions. Substrates measuring 4 cm × 2.5 cm host interdigital capacitive sensors, whereas larger 6 cm × 3.5 cm substrates accommodate inductor‐capacitor (LC) sensors. Each of the six samples undergoes individual dry testing, while LC sensors are additionally tested with the post‐application of artificial saliva and mouthwash liquids. The sensor's characterization involves measurement of impedance and phase angle for all samples. Capacitance is additionally measured for capacitors, and inductance for LC circuits. These assessments are carried out within the frequency range spanning from 1 MHz to 400 MHz. The objective is the development of fully functional electronic components, derived from discarded edible items, fostering sustainable practices, and finding applications in biomedicine. [ABSTRACT FROM AUTHOR]

A novel room temperature capacitive sensor interface circuit is proposed and successfully tested, which uses a modified all-pass filter (APF) architecture combined with a simple series resonant tank circuit with a moderate Q -factor. It is fashioned from a discrete inductor with small dissipation resonating with a grounded capacitor acting as the sensing element to obtain a resolution of Δ C ∼ 2 zF in a capacitance range of 10–30 pF. The circuit converts the change in capacitance to the change in the phase of a carrier signal in a frequency range with a central frequency set up by the tank circuit's resonant frequency and is configured to act as a close approximation of the ideal APF. This cancels out the effects of amplitude modulation when the carrier signal is imperfectly tuned to the resonance. The proposed capacitive sensor interface has been specifically developed for use as a front-end constituent in ultra-precision mechanical displacement measurement systems, such as accelerometers, seismometers, gravimeters and gravity gradiometers, where moving plate grounded air gap capacitors are frequently used. Some other applications of the proposed circuit are possible including the measurement of the electric field, where the sensing capacitor depends on the applied electric field, and cost effective capacitive gas sensors. In addition, the circuit can be easily adapted to function with very small capacitance values (1–2 pF) as is typical in MEMS-based transducers. [ABSTRACT FROM AUTHOR]

The problem addressed in this article focuses on the management of plastic waste, which has experienced a significant increase in recent years, posing challenges in its management and recycling. In addition, the concentration of microplastics in water and their impact on health and the food chain is highlighted. The proposed solution consists of developing a mechatronic system for sorting plastic and metal bottles using capacitive and inductive sensors, respectively. The system demonstrated efficiency in tests, achieving 100% sorting for plastic and metal bottles. The need for bottles to be properly positioned for optimal performance was identified. This work highlights the importance of automation in mechatronic systems and the effectiveness of capacitive and inductive sensors in sorting materials. [ABSTRACT FROM AUTHOR]

Abstract The coupling capacitance between the line and the transducer cannot be ignored when making non‐contact voltage measurements on low‐voltage three‐phase power lines. This leads to an increase in the number of unknown capacitances, and the number of correlatable response voltage equations is less than the number of unknown coupling capacitances. In this paper, a simplified decoupling method is proposed based on the characteristics of triangular three‐phase lines erected in distribution areas. Firstly, the equivalent circuit measured by the voltage sensing mechanism during three‐phase operation is established, and the three‐phase line response voltage equation is derived. Secondly, this paper proposes a three‐phase line response voltage decoupling algorithm after designing the decoupling matrix. Then, this paper uses the least squares method to solve the coefficients in the equations. Finally, the three‐phase voltage fluctuations of the actual low‐voltage stations are simulated by simulation. The measured sensor voltage values are substituted into the algorithm to invert and calculate the three‐phase line voltage. The three‐phase phase error is less than 2°. The amplitude error is less than 1.77%. The experiment verifies the stability and accuracy of the proposed decoupling method.

Flexible pressure sensors with broad linearity range and excellent sensor‐to‐sensor uniformity have attracted unprecedented attention in the electronic skins, human–machine interfaces, and environmental monitoring. However, challenges including poor sensor‐to‐sensor uniformity owing to the randomness of the used nanomaterials or porous structures and saturated response that leads to a restricted linearity range because of structural stiffening have been yet addressed. Herein, a novel dielectric layer based on beetle‐inspired gradient slant structures (GSS) is proposed to endow capacitive pressure sensors with extensive linearity range and excellent sensor‐to‐sensor uniformity. The excellent compressibility of the GSS due to the bending deformation of the slant pillars significantly enhances sensor sensitivity. The broad linearity range comes from the compensation of contact area during sequential contact of the GSS dielectric layer from tall to low slant pillars with electrodes. The high sensor‐to‐sensor uniformity is ascribed to the excellent batch‐to‐batch consistency of prepared GSS via 3D printing‐based fabrication process. Moreover, the proposed GSS‐based pressure sensors present rapid response/recovery, low detection limit, excellent dynamic response, negligible hysteresis, and outstanding long‐term stability. Finally, the excellent applicabilities of proposed capacitive pressure sensors in diverse scenarios including external pressure stimuli detection, a flexible perception array, and a smart insole system are demonstrated. [ABSTRACT FROM AUTHOR]

A novel design of a MEMS (Micro-Electromechanical System) capacitive accelerometer fabricated by surface micromachining, with a structure enabling precise auto-calibration during operation, is presented. Precise auto-calibration was introduced to ensure more accurate acceleration measurements compared to standard designs. The standard mechanical structure of the accelerometer (seismic mass integrated with elastic suspension and movable plates coupled with fixed plates forming a system of differential sensing capacitors) was equipped with three movable detection electrodes coupled with three fixed electrodes, thus creating three atypical tunneling displacement transducers detecting three specific positions of seismic mass with high precision, enabling the auto-calibration of the accelerometer while it was being operated. Auto-calibration is carried out by recording the accelerometer indication while the seismic mass occupies a specific position, which corresponds to a known value of acting acceleration determined in a pre-calibration process. The diagram and the design of the mechanical structure of the accelerometer, the block diagram of the electronic circuits, and the mathematical relationships used for auto-calibration are presented. The results of the simulation studies related to mechanical and electric phenomena are discussed. [ABSTRACT FROM AUTHOR]

Smart wearable devices are extensively utilized across diverse domains due to their inherent advantages of flexibility, portability, and real-time monitoring. Among these, flexible sensors demonstrate exceptional pliability and malleability, making them a prominent focus in wearable electronics research. However, the implementation of flexible wearable sensors often entails intricate and time-consuming processes, leading to high costs, which hinder the advancement of the entire field. Here, we report a pressure and proximity sensor based on oxidized laser-induced graphene (oxidized LIG) as a dielectric layer sandwiched by patterned LIG electrodes, which is characterized by high speed and cost-effectiveness. It is found that in the low-frequency range of fewer than 0.1 kHz, the relative dielectric constant of the oxidized LIG layer reaches an order of magnitude of 10 4 . The pressure mode of this bimodal capacitive sensor is capable of detecting pressures within the range of 1.34 Pa to 800 Pa, with a response time of several hundred milliseconds. The proximity mode involves the application of stimulation using an acrylic probe, which demonstrates a detection range from 0.05 mm to 37.8 mm. Additionally, it has a rapid response time of approximately 100 ms, ensuring consistent signal variations throughout both the approach and withdrawal phases. The sensor fabrication method proposed in this project effectively minimizes expenses and accelerates the preparation cycle through precise control of laser processing parameters to shape the electrode-dielectric layer-electrode within a single substrate material. Based on their exceptional combined performance, our pressure and proximity sensors exhibit significant potential in practical applications such as motion monitoring and distance detection. [ABSTRACT FROM AUTHOR]

This article presents an innovative combination of textile electrical circuits with advanced capabilities of electronic RFID sensors, indicating the revolutionary nature of the development of textronics, which is used in various areas of life, from fashion to medicine. A review of the literature relating to the construction of textronic RFID identifiers and capacitive textronic sensors is performed. Various approaches to measuring capacity using RFID tags are discussed. This article focuses on presenting the concept of a capacitive sensor with an RFID interface, consisting of a microelectronic part and a textile part. The textile part is based on the WL4007 material, where antennas and capacitive sensors are embroidered using SPARKFUN DEV 11791 conductive thread. The antenna is a half-wave dipole designed to operate at a frequency of 860 MHZ. The microelectronic part is sewn to the textile part and consists of a microcontroller, an RFID-integrated circuit and a coupling loop, placed on the PCB. The embroidered antenna is coupled with a loop on the microelectronic module. This article focuses on presenting various designs of textronic electrodes, enabling various types of measurements. Article presents capacitance measurements of individual sensor electrodes, made using a measuring bridge and a built RFID tag. The sensors' capacity measurement results are shown. [ABSTRACT FROM AUTHOR]

Inkjet is a versatile non‐contact printing technique that uses droplets of ink jetted from nozzles to print on a variety of substrates. Although some modern piezoelectric printheads support high viscosity fluids (>10 cP), they are currently expensive and may not be suited for many benchtop experiments in research environment. Here, the design, fabrication by 3D‐printing (no cleanroom processes or silicon micromachining are involved) and testing of a multi‐purpose single‐nozzle piezoelectric dispenser/printhead for medium‐viscosity fluids (10–60 cP) is reported. Custom control electronics are developed to drive the printhead. The design features a 200 μm diameter nozzle, suitable for nL drop generation with solutions containing nm sized particles, thus allowing the deposition of μm thick layers of functional inks in a single printing pass. The inkjet dispenser is first tested with glycerol solutions, resulting in drops of 1.9–3.6 nL with typical drop velocity of 0.5–1.3 m s−1. The developed piezoelectric dispensing system is then demonstrated in the printing of a two‐layer capacitive sensor, using silver nanoparticle ink (conductive ink) and a transparent encapsulant ink (dielectric ink). The reported piezoelectric dispenser design can be optimized for many research purposes, allowing the dispensing of functional chemicals, materials, and biomolecules. [ABSTRACT FROM AUTHOR]

In this study, we employed the finite element software COMSOL Multiphysics® (version 6.0) as a simulation tool to analyze the characteristics of accelerometers with different structures. The initial investigation centered around the 114 µm movable comb electrodes of the ADXL150 accelerometer, known for its single-axis differential capacitive bridge design. These electrodes were chosen as the baseline for our study. Our main goal was to examine how alterations in both the length of the movable comb electrodes and the acceleration rates affect the sensing voltage and displacement of the accelerometers. In this investigation, we aimed to provide a comprehensive understanding of the interplay between electrode length variations and acceleration rates on accelerometer performance. At the outset, our aim was to investigate how varying the length of the electrodes would affect the performance of the accelerometer. We methodically decreased the length of the movable comb electrodes from 114 to 20 µm and increased them from 114 to 129 µm. This range of electrode lengths allowed us to observe and analyze the corresponding variations in sensing voltages across different acceleration rates, namely, 25g, 50g, and 75g. Also, the displacements and von Mises stresses under these different acceleration rates and with lengths of the moveable comb electrodes were also investigated in this study. [ABSTRACT FROM AUTHOR]

Moisture content testing of agricultural products is critical for quality control, processing efficiency and storage management. Testing foxtail millet moisture content ensures stable foxtail millet quality and helps farmers determine the best time to harvest. A differential capacitance moisture content detection device was designed based on STM32 and PCAP01 capacitance digital converter chip. The capacitance method combined with the back-propagation(BP) algorithm and the extreme learning machine(ELM) algorithm was chosen to construct an analytical model for foxtailmilletmoisture content, temperature, and volume duty cycle. This work performs capacitancemeasurements on foxtail millet with different moisture contents, temperatures, and proportions of the measured substance occupying the detection area (that is, the volumetric duty cycle). On this foundation, the sparrow search algorithm (SSA) is used to optimize the BP and ELM models. However, SSA may encounter problems such as falling into local optimization solutions due to the reduction of population diversity in the late iterations. As a consequence, Logistic algorithm is introduced to optimize SSA, making it more appropriate for solving specific problems. Upon comparative analysis, the model predicted using the Logistic-SSA-ELM algorithm was more accurate. The results indicate that the predicted values of prediction set coefficient of determination (RP), prediction set root mean square error (RMSEP) and prediction set ratio performance deviation (RPDP) were 0.7016, 3.7150 and 1.4035, respectively. This algorithm has excellent prediction performance and can be used as a model for detection of foxtail millet moisture content. In view of the important role of foxtail millet moisture content detection in acquisition and storage, it is particularly important to study a nondestructive and fast online real-time detection method. The designed capacitive sensor with differential structure has well stabilization and high accuracy, which can be further studied in depth and gradually move towards the general trend of agricultural development of smart agriculture and precision agriculture. [ABSTRACT FROM AUTHOR]

Summary This paper presents a fully integrated differential charge‐based capacitance measurement (CBCM) circuit designed to detect attoFarads capacitive variations to find airborne particulate matter (PM). This paper presents a novel method for compensating the output offset of the CBCM electronic front‐end in the range of 3.1–3.4 V through the trimming of the bulk voltage of key transistors of the circuit topology. Experimental results on prototypes implemented using a 130‐nm CMOS technology and driven by a 100‐MHz clock confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

An outstanding event related to the understanding of the physics of mechanical sensors occurred and was announced in 1954, exactly seventy years ago. This event was the discovery of the piezoresistive effect, which led to the development of semiconductor strain gauges with a sensitivity much higher than that obtained before in conventional metallic strain gauges. In turn, this motivated the subsequent development of the earliest micromachined silicon devices and the corresponding MEMS devices. The science and technology related to sensors has experienced noteworthy advances in the last decades, but the piezoresistive effect is still the main physical phenomenon behind many mechanical sensors, both commercial and in research models. On this 70th anniversary, this tutorial aims to explain the operating principle, subtypes, input–output characteristics, and limitations of the three main types of mechanical sensor: strain gauges, capacitive sensors, and piezoelectric sensors. These three sensor technologies are also compared with each other, highlighting the main advantages and disadvantages of each one. [ABSTRACT FROM AUTHOR]