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Traditional systems for indoor pressure sensing and human activity recognition (HAR) rely on costly, high-resolution mats and computationally intensive neural network-based (NN-based) models that are prone to noise. In contrast, we design a cost-effective and noise-resilient pressure mat system for HAR, leveraging Velostat for intelligent pressure sensing and a novel hyperdimensional computing (HDC) classifier that is lightweight and highly noise resilient. To measure the performance of our system, we collected two datasets, capturing the static and continuous nature of human movements. Our HDC-based classification algorithm shows an accuracy of 93.19%, improving the accuracy by 9.47% over state-of-the-art CNNs, along with an 85% reduction in energy consumption. We propose a new HDC noise-resilient algorithm and analyze the performance of our proposed method in the presence of three different kinds of noise, including memory and communication, input, and sensor noise. Our system is more resilient across all three noise types. Specifically, in the presence of Gaussian noise, we achieve an accuracy of 92.15% (97.51% for static data), representing a 13.19% (8.77%) improvement compared to state-of-the-art CNNs.

Two‐dimensional (2D) non‐layered materials, along with their unique surface properties, offer intriguing prospects for sensing applications. Introducing mechanical degrees of freedom is expected to enrich the sensing performances of 2D non‐layered devices, such as high frequency, high tunability, and large dynamic range, which could lead to new types of high performance nanosensors. Here, we demonstrate 2D non‐layered nanomechanical resonant sensors based on β‐In2S3, where the devices exhibit robust nanomechanical vibrations up to the very high frequency (VHF) band. We show that such device can operate as pressure sensor with broad range (from 10−3 Torr to atmospheric pressure), high linearity (with a nonlinearity factor as low as 0.0071), and fast response (with an intrinsic response time less than 1 μs). We further unveil the frequency scaling law in these β‐In2S3 nanomechanical sensors and successfully extract both the Young's modulus and pretension for the crystal. Our work paves the way towards future wafer‐scale design and integrated sensors based on 2D non‐layered materials. [ABSTRACT FROM AUTHOR]

Fiber Bragg Grating (FBG) pressure sensor has the advantages of underwater passive, corrosion resistance, light weight, low cost and anti-electromagnetic interference, which has been widely used. This paper first briefly introduces the basic principle of FBG pressure sensing. It then summarizes the development status of FBG writing technology, pressure sensing and sensitizing technology, and temperature compensation technology. Next, it summarizes the application progress of FBG pressure sensor in the fields of ocean depth, lake level measurement, oil and gas pipeline pressure measurement, and rock and soil pressure monitoring in recent years. Finally, the FBG pressure sensing technology is prospected.

[Display omitted] • Biomass-based carbon aerogels with low volume shrinkage were fabricated. • Zn (II) crosslinking significantly improved the carbon retention rate during carbonization. • High compressive strength, superelasticity and excellent fatigue resistance were achieved. • The piezoresistive sensor exhibited high sensitivity, fast response and good repeatability. • The assembled wearable sensor was successfully applied for detecting human motions. Elastic carbon aerogels have promising applications in the field of wearable sensors. Herein, a new strategy for preparing carbon aerogels with excellent compressive strength and strain, shape recovery, and fatigue resistance was proposed based on the structure design and carbonization optimization of nanocellulose-based precursor aerogels. By the combination of directional freezing and zinc ion cross-linking, bacterial cellulose (BC)/alginate (SA) composite aerogels with high elasticity and compressive strength were first achieved. The existance of zinc ions also significantly improved the carbon retention rate and inhibited structural shrinkage, thus making the carbon aerogels retain ultra-high elasticity and fatigue resistance after compression. Moreover, the carbon aerogel possessed excellent piezoresistive pressure sensing performance with a wide detection range of 0–7.8 kPa, high sensitivity of 11.04 kpa-1, low detection limit (2 % strain), fast response (112 ms), and good durability (over 1,000 cycles). Based on these excellent properties, the carbon aerogel pressure sensors were further successfully used for human motion monitoring, from joint motion to and speech recognition. [ABSTRACT FROM AUTHOR]

There is an extensive need for surface sensors for applications such as tactile sensing for robotics, damage and strain detection for structural health monitoring and leak detection for buried structures. One type of surface sensor is electrical impedance tomography (EIT)-based sensing skins, which use electrically conductive coatings applied on the object's surface to monitor physical or chemical phenomena on the surface. In this article, we propose a sensing skin with two electrically coupled layers separated by an insulator. Based on electrical measurements, the spatial distribution of the electrical coupling between the layers is estimated. This coupling is sensitive to both the pressure distribution on the surface and water entering between the layers through a leak. We present simulations and experimental studies to evaluate the feasibility of the proposed method for pressure sensing and leak detection. The results support the feasibility of the proposed method for both of these applications. [ABSTRACT FROM AUTHOR]

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Multifunctional sensors have played a crucial role in constructing high-integration electronic networks. Most of the current multifunctional sensors rely on multiple materials to simultaneously detect different physical stimuli. Here, we demonstrate the large piezo-pyroelectric effect in ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals for simultaneous pressure and temperature sensing. The outstanding piezoelectric and pyroelectric properties of PMN-PT result in rapid response speed and high sensitivity, with values of 46 ms and 28.4 nA kPa−1 for pressure sensing, and 1.98 s and 94.66 nC °C−1 for temperature detection, respectively. By leveraging the distinct differences in the response speed of piezoelectric and pyroelectric responses, the piezo-pyroelectric effect of PMN-PT can effectively detect pressure and temperature from mixed-force thermal stimuli, which enables a robotic hand for stimuli classification. With appealing multifunctionality, fast speed, high sensitivity, and compact structure, the proposed self-powered bimodal sensor therefore holds significant potential for high-performance artificial perception. [ABSTRACT FROM AUTHOR]

Abstract Two‐dimensional (2D) non‐layered materials, along with their unique surface properties, offer intriguing prospects for sensing applications. Introducing mechanical degrees of freedom is expected to enrich the sensing performances of 2D non‐layered devices, such as high frequency, high tunability, and large dynamic range, which could lead to new types of high performance nanosensors. Here, we demonstrate 2D non‐layered nanomechanical resonant sensors based on β‐In2S3, where the devices exhibit robust nanomechanical vibrations up to the very high frequency (VHF) band. We show that such device can operate as pressure sensor with broad range (from 10−3 Torr to atmospheric pressure), high linearity (with a nonlinearity factor as low as 0.0071), and fast response (with an intrinsic response time less than 1 μs). We further unveil the frequency scaling law in these β‐In2S3 nanomechanical sensors and successfully extract both the Young's modulus and pretension for the crystal. Our work paves the way towards future wafer‐scale design and integrated sensors based on 2D non‐layered materials.

Arterial Vascular smooth muscle cells (VSMCs) play a central role in the onset and progression of atherosclerosis. Upon exposure to pathological stimuli, they can take on alternative phenotypes that, among others, have been described as macrophage like, or foam cells. VSMC foam cells make up >50% of all arterial foam cells and have been suggested to retain an even higher proportion of the cell stored lipid droplets, further leading to apoptosis, secondary necrosis, and an inflammatory response. However, the mechanism of VSMC foam cell formation is still unclear. Here, it is identified that mechanical stimulation through hypertensive pressure alone is sufficient for the phenotypic switch. Hyperspectral stimulated Raman scattering imaging demonstrates rapid lipid droplet formation and changes to lipid metabolism and changes are confirmed in ABCA1, KLF4, LDLR, and CD68 expression, cell proliferation, and migration. Further, a mechanosignaling route is identified involving Piezo1, phospholipid, and arachidonic acid signaling, as well as epigenetic regulation, whereby CUT&Tag epigenomic analysis confirms changes in the cells (lipid) metabolism and atherosclerotic pathways. Overall, the results show for the first time that VSMC foam cell formation can be triggered by mechanical stimulation alone, suggesting modulation of mechanosignaling can be harnessed as potential therapeutic strategy. [ABSTRACT FROM AUTHOR]

Flexible electronic skin (e-skin) for mobile health applications urgently requires wearable pressure-gas sensors, which can be used for body motion detection and identification of environmental gas targets. However, applying pressure-gas sensors to e-skin has always faced challenges of high sensitivity, wide detection range, and high stability. Herein, a novel multifunctional pressure-gas sensor was proposed that 2D reduced graphene oxide (rGO) with 1D copper nanowires (CuNWs) and silver nanowires (AgNWs) form 3D porous composite aerogels by self-assembly and in situ oxidation CuNWs convert to Cu x O nanowires (Cu x ONWs), which ensures efficient electron transfer and sufficient gas adsorption sites. Furthermore, the polydimethylsiloxane (PDMS) layer dramatically improved the electro-mechanical properties of the sensing elastomer. The rGO-Cu x ONW-AgNW/PDMS (GCOAP) sensing elastomer realizes bi-directional resistive response of pressure (falling) and gas (rising), and is capable of fast response (66 ms) to large pressures (1600 kPa) with high sensitivity (1.405 kPa−1) and specific identification of hazardous NH 3 gas at room temperature. [ABSTRACT FROM AUTHOR]

In this study, we developed a novel wireless, passive pressure-sensing method functional at cryogenic temperatures (−196 °C). The currently used pressure sensors are inconvenient and complicated in cryogenic environments for their weak low-temperature tolerances and long wires for power supply and data transmission. We propose a novel pressure-sensing method for cryogenic applications by only using low-temperature-tolerant passive devices. By innovatively integrating a magnetoresistor (MR) on a backscattering antenna, the pressure inside a cryogenic environment is transferred to a wirelessly obtainable return loss. Wireless passive measurement is thus achieved using a backscattering method. In the measurement, the pressure causes a relative displacement between the MR and a magnet. The MR's resistance changes with the varied magnetic field, thus modulating the antenna's return loss. The experimental results indicate that our fabricated sensor successfully identified different pressures, with high sensitivities of 4.3 dB/MPa at room temperature (24 °C) and 1.3 dB/MPa at cryogenic temperature (−196 °C). Additionally, our method allows for simultaneous wireless readings of multi sensors via a single reading device by separating the frequency band of each sensor. Our method performs low-cost, simple, robust, passive, and wireless pressure measurement at −196 °C; thus, it is desirable for cryogenic applications. [ABSTRACT FROM AUTHOR]

During vapour phase reflow soldering used in electronics manufacturing, the process control of ovens is usually based on temperature measurements, which can be insufficient due to the saturation differences in the temperature and the vapour concentration. Therefore, the ovens use extended cycle times for process identification to ensure the proper formation of solder joints. This study offers a solution to eliminate the idle time by investigating the hydrostatic pressure conditions in the process zone. A pressure measurement system was developed for vapour phase soldering ovens which can monitor the vapour pressure changes by a gauge-type pressure sensor with fused temperature measurement. It works as an IoT-enabled node for data logging and subsequent control. The fusion of the hydrostatic pressure values with the temperature values allowed us to identify and reduce the idle time by approximately 60 s, which is 15–20% of the total soldering cycle time. This increases the oven's yield by 15–20%, reduces the system's power consumption by 15–20%, and reduces time above liquidus of the solder by ∼35%. The presented method could enhance the more sustainable electronics production according to the Sustainability Development and could improve the quality and reliability of the lead-free solder joints.

In this paper, a photonic skin sensor based on a balloon-shaped optical fiber structure cascading a Fiber Bragg Grating (FBG) is proposed, which can simultaneously sense pressure and temperature. When the photonic skin feels pressure, the built-in polymer micro-cap is squeezed, causing a change in the radius of the balloon-shaped structure. At the same time, the capillary-enclosed FBG can be used for temperature compensation. The pressure sensitivity of the photon skin sensor can reach 6.556 nm/mN in the range of 0-0.5 mN and the temperature sensitivity can reach -0.192 nm/°C in the range of 30-50 °C. The demodulation of the dual parameter matrix shows that the error rates of pressure and temperature measurements are less than 0.5% and 2.01%, respectively. On this basis, the sensor is applied to robotic arm-assisted puncture experiment detection, and the five states of the puncture process are analyzed. Based on the backpropagation (BP) neural network for repeated training, the results show that its accuracy remains at 98.7%, indicating that the sensor has good robustness. The development of this sensor shows application potential in the field of robotic intelligent skin in the future.

Abstract Arterial Vascular smooth muscle cells (VSMCs) play a central role in the onset and progression of atherosclerosis. Upon exposure to pathological stimuli, they can take on alternative phenotypes that, among others, have been described as macrophage like, or foam cells. VSMC foam cells make up >50% of all arterial foam cells and have been suggested to retain an even higher proportion of the cell stored lipid droplets, further leading to apoptosis, secondary necrosis, and an inflammatory response. However, the mechanism of VSMC foam cell formation is still unclear. Here, it is identified that mechanical stimulation through hypertensive pressure alone is sufficient for the phenotypic switch. Hyperspectral stimulated Raman scattering imaging demonstrates rapid lipid droplet formation and changes to lipid metabolism and changes are confirmed in ABCA1, KLF4, LDLR, and CD68 expression, cell proliferation, and migration. Further, a mechanosignaling route is identified involving Piezo1, phospholipid, and arachidonic acid signaling, as well as epigenetic regulation, whereby CUT&Tag epigenomic analysis confirms changes in the cells (lipid) metabolism and atherosclerotic pathways. Overall, the results show for the first time that VSMC foam cell formation can be triggered by mechanical stimulation alone, suggesting modulation of mechanosignaling can be harnessed as potential therapeutic strategy.

There is an extensive need for surface sensors for applications such as tactile sensing for robotics, damage and strain detection for structural health monitoring and leak detection for buried structures. One type of surface sensor is electrical impedance tomography (EIT)-based sensing skins, which use electrically conductive coatings applied on the object’s surface to monitor physical or chemical phenomena on the surface. In this article, we propose a sensing skin with two electrically coupled layers separated by an insulator. Based on electrical measurements, the spatial distribution of the electrical coupling between the layers is estimated. This coupling is sensitive to both the pressure distribution on the surface and water entering between the layers through a leak. We present simulations and experimental studies to evaluate the feasibility of the proposed method for pressure sensing and leak detection. The results support the feasibility of the proposed method for both of these applications.

Abstract Mechanical forces control the function of organisms and mediate the interaction between biological systems and their environments. Knowledge of these forces will increase the understanding of biological processes and can support the development of novel diagnostic and therapeutic procedures. Although techniques like atomic force microscopy and droplet insertion method allow measuring forces over a broad range of values, they are invasive and lack versatility. A promising way to overcome these hurdles is luminescent nanomanometry. Quantum dots (QDs) specifically have optical properties that depend on their size because of the quantum confinement, which makes them responsive to applied forces. Yet, a fine understanding of how fundamental parameters affect the response to applied stress is required before a QD family can be credibly proposed as luminescent nanomanometers. Here, a thorough study is conducted on how size and stoichiometry affect the nanomanometry performance of CuInS2 QDs. The studied QDs feature pressure‐dependent photoluminescence in the red/near‐infrared range, which can enable the measurement of mechanical forces in the range of physiological relevance in a remote and minimally invasive way. It is shown that tuning size and stoichiometry can simultaneously enhance the CuInS2 QDs’ brightness and response to applied pressure, thus providing guidelines for better luminescent nanomanometers.

Multifunctional sensors have played a crucial role in constructing high-integration electronic networks. Most of the current multifunctional sensors rely on multiple materials to simultaneously detect different physical stimuli. Here, we demonstrate the large piezo-pyroelectric effect in ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals for simultaneous pressure and temperature sensing. The outstanding piezoelectric and pyroelectric properties of PMN-PT result in rapid response speed and high sensitivity, with values of 46 ms and 28.4 nA kPa−1 for pressure sensing, and 1.98 s and 94.66 nC °C−1 for temperature detection, respectively. By leveraging the distinct differences in the response speed of piezoelectric and pyroelectric responses, the piezo-pyroelectric effect of PMN-PT can effectively detect pressure and temperature from mixed-force thermal stimuli, which enables a robotic hand for stimuli classification. With appealing multifunctionality, fast speed, high sensitivity, and compact structure, the proposed self-powered bimodal sensor therefore holds significant potential for high-performance artificial perception.

Traditional systems for indoor pressure sensing and human activity recognition (HAR) rely on costly, high-resolution mats and computationally intensive neural network-based (NN-based) models that are prone to noise. In contrast, we design a cost-effective and noise-resilient pressure mat system for HAR, leveraging Velostat for intelligent pressure sensing and a novel hyperdimensional computing (HDC) classifier that is lightweight and highly noise resilient. To measure the performance of our system, we collected two datasets, capturing the static and continuous nature of human movements. Our HDC-based classification algorithm shows an accuracy of 93.19%, improving the accuracy by 9.47% over state-of-the-art CNNs, along with an 85% reduction in energy consumption. We propose a new HDC noise-resilient algorithm and analyze the performance of our proposed method in the presence of three different kinds of noise, including memory and communication, input, and sensor noise. Our system is more resilient across all three noise types. Specifically, in the presence of Gaussian noise, we achieve an accuracy of 92.15% (97.51% for static data), representing a 13.19% (8.77%) improvement compared to state-of-the-art CNNs.

The practical applications of hydrogel-based sensors are limited by their low mechanical strength, insufficient sensitivity and machining difficulties caused by electrically conductive fillers. It is of great practical importance for facile preparation of hydrogel sensor combined with excellent mechanical properties and conductive sensitivity. In this work, a series of ion-conductive hybrid hydrogels based on in-situ polymerized polyacrylamide with double and triple network structures have been fabricated via both chemical and physical cross-linking. The triple network structured hydrogels achieve the tensile strength of 2.105 MPa and compression strength of 57.56 MPa, which are much higher than those of hydrogels with double network due to the established energy dissipation gradient. The reversible non-covalent cross-linking in the network also leads a relatively fast recovery in tensile cycle tests and double compression tests, enabling the excellent stability of strain sensing in the durability test. The hydrogels show the tensile resistance sensitivity factor of 0.9352 at 0–120% strain and a high pressure sensitivity factor of 5.134 kPa−1 with the pressure ranged from 0 to 6 kPa. The hydrogels are also assembled as flexible sensors for human motion monitoring, and the signals of motions can be distinguished by different resistance variation values and certain curve shape, showing the potential of applications on flexible device and human-machine interface.

Polydimethylsiloxane (PDMS) based soft polymer optical fibers (POFs) have recently demonstrated their intriguing potential for different sensing applications like strain or temperature sensing. Recent studies have elaborated on the sensing capability of PDMS POFs, yet the in-depth analysis of the processing-property relationship of PDMS POFs remains unexplored. A straightforward processing strategy was developed for core only PDMS POFs and PDMS/THV (terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride) core/clad POFs. The optimization of chemical formulations and process parameters such as curing temperature and curing time provided the development of POFs with tailored mechanical and optical properties. The tensile modulus of the moulded PDMS POFs could be tuned in the range of 0.2–3.0 MPa, with attenuations as low as 0.11 dB/cm in the near infrared region (NIR). Furthermore, the load and pressure sensing capability of the PDMS POFs was demonstrated with sensitivity to loads as low as 0.1 N and highly accurate pressure sensing up to 300 kPa. The systematic approach presented in this study enables the processing of elastic PDMS POFs with tunable mechanical and optical properties, which can be tailored to suitable sensing applications in the field of healthcare monitoring, biomedicine, and soft robotics.

This article is devoted to the study of the correlation between the emotional state of a person and the posture of his or her body in the sitting position. In order to carry out the study, we developed the first version of the hardware-software system based on a posturometric armchair, allowing the characteristics of the posture of a sitting person to be evaluated using strain gauges. Using this system, we revealed the correlation between sensor readings and human emotional states. We showed that certain readings of a sensor group are formed for a certain emotional state of a person. We also found that the groups of triggered sensors, their composition, their number, and their location are related to the states of a particular person, which led to the need to build personalized digital pose models for each person. The intellectual component of our hardware–software complex is based on the concept of co-evolutionary hybrid intelligence. The system can be used during medical diagnostic procedures and rehabilitation processes, as well as in controlling people whose professional activity is connected with increased psycho-emotional load and can cause cognitive disorders, fatigue, and professional burnout and can lead to the development of diseases. [ABSTRACT FROM AUTHOR]

Portable, wearable electronic devices have spurred the rapid development of flexible and stretchable energy harvesting/storage devices with high energy density, superior mechanical stability, and long cycle life. Micro-supercapacitor (MSC) has attracted wide interest due to their advantages of high power density, rapid charge and discharge, and long cycle life. Fabrication of flexible supercapacitors based on laser induced graphene (LIG) has shown strong advantages and potential for flexible sensor power supply. The purpose of this paper is to propose and develop a laser induced flexible micro-supercapacitor (FMSC) for pressure sensors. FMSC is manufactured from a planar forked finger electrode made of graphene induced by CO2 laser radiation commercial Polyimide (PI) film and PVA polymer gel electrolyte. The FMSCs prepared by this method exhibit good electrochemical properties and excellent mechanical properties. The microscopic morphology of LIG was investigated using SEM, and the optimal laser-induced power was determined to be 12.5%. In this paper, a novel fork-finger electrode pattern was applied to improve the performance of FMSCs by optimizing the structure of planar interdigital electrodes, and the FMSCs prepared at 12.5% power showed excellent supercapacitance performance at a voltage window of 0.8 V with a specific capacitance of 2.21 mF/cm2. The FMSCs were made by assembling commercial PI films, PVA, and H3PO4 simple materials, which makes it possible to prepare FMSCs at low cost and high efficiency based on laser direct writing technology. FMSCs provide energy to the flexible sensors and continuously collect energy to charge FMSCs through an integrated flexible energy harvester, which makes FMSCs promising for flexible self-powered wireless sensing platforms.

This paper discusses the fabrication and characterization of cyclic olefin copolymer (COC)-based pseudo-piezoelectric materials (piezoelectrets) with exceptionally high piezoelectric activity, and their potential use in sensing applications. Piezoelectrets that utilize a novel microhoneycomb structure to achieve high piezoelectric sensitivity are carefully engineered and fabricated at a low temperature using a supercritical CO2-assisted assembly. The quasistatic piezoelectric coefficient d33 of the material can reach up to 12,900 pCN−1 when charged at 8000 V. The materials also exhibit excellent thermal stability. The charge build-up in the materials and the actuation behavior of the materials are also investigated. Finally, applications of these materials in pressure sensing and mapping and in wearable sensing are demonstrated. [ABSTRACT FROM AUTHOR]

We theoretically investigate the defect mode transmittance of light waves in superconductor–semiconductor photonic crystals and its pressure-sensing dependence. The photonic crystal is composed of alternating superconducting and semiconducting slabs and a defect locates at the center of this structure. Two trapezoid waveguides are fixed at both sides of the crystal, which induces the hydrostatic pressure applied and beams transmitted simultaneously. The resonant wavelength variation in the defect mode is directly proportional to the pressure applied on the system in the near-IR region, which can be utilized for linear pressure sensors in the cryogenic environment. Pressure sensitivity reaches a high value of 2.6 nm/GPa, which is higher than that in the study based on the reflection spectra. The sensitivity coefficient may be modulated by the environment temperature as well. This study has potential regarding pressure-light-wave sensors. [ABSTRACT FROM AUTHOR]

In this study, we developed a novel wireless, passive pressure-sensing method functional at cryogenic temperatures (−196 °C). The currently used pressure sensors are inconvenient and complicated in cryogenic environments for their weak low-temperature tolerances and long wires for power supply and data transmission. We propose a novel pressure-sensing method for cryogenic applications by only using low-temperature-tolerant passive devices. By innovatively integrating a magnetoresistor (MR) on a backscattering antenna, the pressure inside a cryogenic environment is transferred to a wirelessly obtainable return loss. Wireless passive measurement is thus achieved using a backscattering method. In the measurement, the pressure causes a relative displacement between the MR and a magnet. The MR’s resistance changes with the varied magnetic field, thus modulating the antenna’s return loss. The experimental results indicate that our fabricated sensor successfully identified different pressures, with high sensitivities of 4.3 dB/MPa at room temperature (24 °C) and 1.3 dB/MPa at cryogenic temperature (−196 °C). Additionally, our method allows for simultaneous wireless readings of multi sensors via a single reading device by separating the frequency band of each sensor. Our method performs low-cost, simple, robust, passive, and wireless pressure measurement at −196 °C; thus, it is desirable for cryogenic applications.

The existing instruments for aerodynamic pressure measurements are usually built around an array of discrete pressure sensors, placed in the same housing together with a few discrete temperature sensors. However, this approach is limiting, especially regarding miniaturization, sensor matching, and thermal coupling. In this work, we intend to overcome these limitations by proposing a novel MEMS multisensor chip, which has a monolithically integrated matrix of four piezoresistive MEMS pressure-sensing elements and two resistive temperature-sensing elements. After finishing the preliminary chip design, we performed computer simulations in order to assess its mechanical behavior when measured pressure is applied. Subsequently, the final chip design was completed, and the first batch was fabricated. The used technological processes included photolithography, thermal oxidation, diffusion, sputtering, micromachining (wet chemical etching), anodic bonding, and wafer dicing.

[Display omitted] • A multifunctional MXene-coated textile was prepared by a facile dip-coating method. • Lightly cross-linked PDMS network endowed the textile stable adhesive properties. • The adhesive textile showed good electro-/photo-thermal conversion performance. • The smart textile showed good electromagnetic interference shielding properties. • The adhesive textile showed stable pressure-sensing response for motion detection. Adhesion between flexible devices and skin surface facilitates portability of devices and reliable signal acquisition from human body, which is essential for medical therapy devices or monitoring systems. Here, we utilize a simple, cost-effective, and scalable layer-by-layer dip-coating method to fabricate a skin-adhesive multifunctional textile-based device, consisting of three parts: low-cost and easily available airlaid paper (AP) substrate, conductive MXene sensitive layer, and adhesive polydimethylsiloxane (PDMS). The adhesive layer of lightly cross-linked PDMS enables the device to form conformal contact with skin even during human joint bending. The smart textile device exhibits excellent electro-thermal and photo-thermal conversion performance with good cycling stability and tunability. Furthermore, the textile electronics show good electromagnetic interference (EMI) shielding properties due to the good electrical conductivity, as well as sensitive and stable pressure sensing properties for human motion detection. Consequently, this efficient strategy provides a possible way to design multifunctional and wearable electronic textiles for medical applications. [ABSTRACT FROM AUTHOR]

In the era of intelligent sensing, there is a huge demand for flexible pressure sensors. High sensitivity is the primary requirement for flexible pressure sensors, whereas pressure response range and resolution, which are also key parameters of sensors, are often ignored, resulting in limited applications of flexible pressure sensors. This paper reports a flexible capacitive pressure sensor based on a double-sided microstructure porous dielectric layer. First, a porous structure was developed in the polymer dielectric layer consisting of silicon rubber (SR)/NaCl/carbon black (CB) using the dissolution method, and then hemisphere microstructures were developed on both sides of the layer by adopting the template method. The synergistic effect of the hemispheric surface microstructure and porous internal structure improves the deformability of the dielectric layer, thus achieving high sensitivity (3.15 kPa−1), wide response range (0–200 kPa), and high resolution (i.e., the minimum pressure detected was 27 Pa). The proposed sensing unit and its array have been demonstrated to be effective in large-area pressure sensing and object recognition. The flexible capacitive pressure sensor developed in this paper is highly promising in applications of robot skin and intelligent prosthetic hands. [ABSTRACT FROM AUTHOR]

[Display omitted] • The application of this pressure-sensitive hydrogel can effectively avoid the secondary injury of the wound. • This hydrogel dressing significantly promotes full-thickness skin wound healing. • The properties of hydrogel are improved through the regulation of chemical structure for Ionic liquid monomers. Pressure ulcer is a common chronic injury in the bedridden population. The wound is easily subjected to secondary pressure injury due to the inconvenient mobility of patients, which greatly prolongs the hospital stay of patients and is highly prone to wound infection or other complications. It is urgent to develop a multifunctional wound dressing with pressure sensing, real-time monitoring, and wound therapy to overcome the secondary pressure injury during treatment. Here, a polyvinyl alcohol/acrylamide-ionic liquid hydrogel dressing is designed based on the antibacterial property and electrical conductivity of imidazolidine ionic liquids. Compared with existing pressure-sensing hydrogels, the hydrogel exhibits extremely high pressure sensitivity (9.19 kPa−1). Meanwhile, the good real-time responsiveness, stable signal output as well as excellent mechanical properties enable the hydrogel to monitor human movement on a large scale, and transmit the pressure status of patient wounds to nursing staff in a timely manner to avoid secondary pressure injuries. In addition, this hydrogel dressing exhibits a wide range of antibacterial activities against Gram-negative and Gram-positive bacteria as well as fungi, and has a significant therapeutic effect on full-thickness skin wounds by inhibiting wound infection, rapidly eradicating inflammation, promoting proliferation and tissue remodeling. This multifunctional hydrogel dressing opens a therapeutic and regulatory two-pronged strategy avenue through chronic wound management and pressure sensing monitoring. [ABSTRACT FROM AUTHOR]

Soft robotic and medical devices will greatly benefit from stretchable and compliant pressure sensors that can detect deformation and contact forces for control and task safety. In addition to traditional 2D buckling via planar substrates, 3D buckling via curved substrates has emerged as an alternative approach to generate tunable and highly convoluted hierarchical wrinkle morphologies. Such wrinkles may provide advantages in pressure sensing, such as increased sensitivity, ultra-stretchability, and detecting changing curvatures. In this work, we fabricated stretchable sensors using wrinkled MXene electrodes obtained from 3D buckling. We then characterized the sensors' performance in detecting strain, pressure, and vibrations. The fabricated wrinkled MXene electrode exhibited high stretchability of up to 250% and has a strain sensitivity of 0.1 between 0 and 80%. The fabricated bilayer MXene pressure sensor exhibited a pressure sensitivity of 0.935 kPa−1 and 0.188 kPa−1 at the lower (<0.25 kPa) and higher-pressure regimes (0.25 kPa–2.0 kPa), respectively. The recovery and response timing of the wrinkled MXene pressure sensor was found to be 250 ms and 400 ms, respectively. The sensor was also capable of detecting changing curvatures upon mounting onto an inflating balloon. [ABSTRACT FROM AUTHOR]

Fiber-optic sensors are a powerful tool to investigate physical properties like temperature, strain, and pressure. Such properties make these sensors interesting for many applications including biomedical applications. Fiber sensors are also a great platform for distributed sensing by using the principles of optical frequency domain reflectometry. Distributed sensing is becoming more and more used to achieve high-resolution measurements and to map physical properties of biomaterials at small scale, thus obtaining 2D and 3D mapping of a particular area of interest. This work aims at building and investigating a 2D sensing carpet based on a distributed fiber sensing technique, to map local pressure applied to the carpet. The two-dimensional mapping is obtained by embedding a single-mode optical fiber inside a soft silicone carpet. The fiber has been bent and arranged in a specific configuration characterized by several parallel lines. Different fiber fixation methods have been investigated by means of a comparative analysis to perform better characterization and to achieve a more precise response of the carpet. The best pressure sensitivity coefficient (0.373 pm/kPa or considering our setup 1.165 nm/kg) was detected when the fiber was fully embedded inside the silicone carpet. This paper demonstrates the possibility of mapping a 2D distributed pressure over a surface with a resolution of 2 mm by 2 mm. The surface of investigation is 2 cm by 6 cm, containing 310 sensing points. The sensing carpet has been validated selecting several preferential positions, by testing the consistency of the results over different portions of the carpet. [ABSTRACT FROM AUTHOR]

• Multifunctional sensors for synchronous pressure/biopotential acquisition wore developed. • The developed multifunctional sensors can respond to pressure and biopotential signals synchronously and recognize human movements. • The chemical polymerization mechanism of PANI and the response mechanism of the conductive film to pressure were analyzed. • Provide methods and basis for the study of the dynamic noise mechanism at the electrode/electrolyte interface. Surface biopotential dry electrodes are an important part of long-term healthcare health monitoring systems. During long-term dynamic monitoring, pressure fluctuations between the skin/electrode can affect the acquisition of ECG signals and reduce the stability of the system. In this study, by printing an interactive circuit on the back of the Fructus xanthii-inspired barb structure (FXbs) Ag/AgCl-TPU dry electrodes, the micro-nanocone PANI/PMMA flexible conductive film is encapsulated on the back of the FXbs dry electrode, and a multifunctional sensor and monitoring clothing are constructed, which can synchronously collect pressure signals and ECG signals, and can monitor human movements. In the simulation instrument and human skin surface, the influence of pressure fluctuation on the quality of ECG signal acquisition under different pressure, speed, and motion states is explored. In the simulation instrument, when the change rate of piezoresistive reaches the maximum value of 51.41 %, the fluctuation range of ECG is the smallest, which is 0.99 mV. On the surface of human skin, the change rate of piezoresistive and the fluctuation range of ECG in the turning state reach the maximum, which is 5.02 % and 5.99 mV, respectively. It can provide a reference to study the influence of pressure fluctuation on ECG signals on the surface of human skin, and at the same time, it can provide an experimental method and basis for the study of the dynamic noise mechanism at the electrode/electrolyte interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifunctional MXene/cellulose film was prepared for EMI shielding and energy management. • PCM has the strength of 235 MPa, conductivity of 9288 S·m−1, and EMI SE of 44.6 dB. • The Joule heating temperature of the laminated paper was 610 °C at a voltage of 5 V. • PCM has a low infrared emissivity, enabling infrared stealth. • PCM achieved heating visualization function, human motion monitoring, and light-driven actuation. In the era of increasing reliance on electronic devices, the development of flexible smart composite films that offer multifunctional capabilities such as electromagnetic shielding, sensing, infrared stealth, and autonomous heating is becoming increasingly significant. In this study, we fabricated polydopamine-modified cellulose scaffold/MXene composite films (PCM) using a densification strategy, resulting in films with a thickness of only 33 μm, outstanding tensile strength of 235.28 MPa, and excellent electromagnetic shielding effectiveness of 44.6 dB. The PCM also demonstrates remarkable electrothermal performance, reaching temperatures of up to 610 °C at 5 V, and exhibits excellent photo-thermal conversion performance, along with good cycling stability and tunability. Additionally, the PCM's low infrared emissivity provides it with exceptional infrared stealth capabilities, effectively concealing a high surface temperature ranging from 250 °C to 25 °C. The PCM's ability to detect human body movement and light-driven actuation for bionic motions underscores its flexibility and utility as a sensor. Therefore, this efficient and versatile approach provides a promising method for synthesizing multifunctional MXene-based composite films, achieving satisfactory mechanical properties, high electromagnetic interference shielding, and effective thermal management for wearable smart devices and military applications. [ABSTRACT FROM AUTHOR]

The high demand for pressure devices with miniaturization and a wide bearing range has encouraged researchers to explore new high-performance sensors from different approaches. In this study, a sensitive element based on graphene in-plane compression properties for realizing pressure sensing is experimentally prepared using microelectromechanical systems (MEMS) fabrication technology; it consists of a 50 µm thick, 1400 µm wide square multilayer component membrane and a graphene monolayer with a meander pattern. The prepared sample is extensively characterized and analyzed by using various techniques, including atomic force microscopy, Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, COMSOL finite element method, and density functional theory. The sensing performance of the new pressure sensor based on the sensitive element are obtained by theoretical analysis for electromechanical measurements of the sensitive element before and after low-temperature annealing in atmosphere. Results demonstrate that atmospheric annealing at 300 °C enhances the pressure sensing sensitivity by 4 times compared to pristine graphene without annealing, which benefits from the desorption of hydroxyl groups on the graphene surface during annealing. The sensitivity is comparable and even better than that of previous sensors based on graphene in-plane properties. Our results provide new insights into realizing high-performance MEMS devices based on 2D sensitive materials. [ABSTRACT FROM AUTHOR]

A simple and cost-effective calibration procedure for piezoresistive ink tactile pressure sensors is crucial for their use in geotechnical research applications. Such a procedure should be applicable in field conditions and require a minimum amount of equipment. The paper describes a new method for calibrating tactile pressure sensors with 8-bit sensels' output. The method is based on the approximation of a single sensel output and consideration of multiple calibration patches. The advantage of the developed method is using local high-pressure zones in calibration patches. The developed method has been successfully applied in calibration of two 5051-350 Tekscan sensors by means of three dead weights: 2 kg, 5 kg and 10 kg. One calibrated sensor was new, and another one had been previously used in the harsh environment of the ice tank in the experiment with model ice. The calibration curves for these two sensors did not reveal a significant difference. For 72% of the 150 obtained load patches in calibration, the absolute discrepancy of actual and calibrated load occurred to be less than 5%. [ABSTRACT FROM AUTHOR]

Although bio-based sensing materials have a wide range of applications in the field of pressure detection, they still need to improve their sensitivity, detection limit and hysteresis. This paper studied the relationship between the 3D pore structure and sensing performance under dynamics. Using Balsa wood as the substrate, CWA/TPU aerogel and its sensor were prepared with lightweight, compressibility, highly sensitivity, wide-detection, and low-hysteresis. Meanwhile, the brittleness problem of the carbonized aerogel was solved by uniformly attaching TPU to the aerogel interface. In this paper, the 3D structure of CWA/TPU aerogel during compression was reconstructed by Micro-XCT technology, and the results show that the sensitivity of the bio-based carbonized material is directly proportional to the porosity and inversely proportional to the aspect ratio. This CWA/TPU aerogel pressure sensor has a high sensitivity of 76.18 kPa -1 in a wide detection limit of 0.6 Pa-100 kPa, 90 % supercompression strain, ±7.4 % low hysteresis and outstanding stability over 10,000 cycles. And the sensor can detect different ranges of pressure strains and has great potential for future applications in physiological signal monitoring, action recognition, and sports training., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The occurrence of bedsores in Ghanaian hospitals, elderly homes or care homes is especially high among patients or people who are incapacitated and cannot move or turn on their own, and who happen to remain in a particular posture for a very long time. Patients in coma, those operated on and for that matter in critical state, and patients confined to wheelchairs are primary examples. Constant pressure on some parts of the body leads to the occurrence of pressure sores or ulcers. This paper seeks to implement a Bedsore Easing System (BeSoSys) that integrate several embedded hardware components, a database and software to reduce the occurrence of bedsores. These embedded hardware components include the Bed Device Unit (BDU), the Pocket Device Unit (PDU), a pressure or weight sensor, a temperature sensor, and an inflation-deflation device. The BDU is fitted into the bed of the patient or on the surface of skin contact of the patient. The PDU is assigned to nurses or caretakers to serve as an alarm system for patient repositioning depending on situation. All activities in the Bedsore Easing System are logged into a database for future references. A bedridden patient exerts constant pressure on the bony protrusions of the body, and this causes bedsores. It was found out during the research that in Ghana, the nurses or caretakers used to turn and massage patients at some random time intervals as a way of preventing bedsores. This traditional way of turning and massaging patients is not only tedious but also ineffective. This paper seeks to provide easy, better, and effective solution to ease bedsores. The BeSoSys intends to prevent the occurrence of bedsores hence the alleviation of bedsore complications

We present a solution for intelligent posture training based on accurate, real-time sitting posture monitoring using the LifeChair IoT cushion and supervised machine learning from pressure sensing and user body data. We demonstrate our system's performance in sitting posture and seated stretch recognition tasks with over 98.82% accuracy in recognizing 15 different sitting postures and 97.94% in recognizing six seated stretches. We also show that user BMI divergence significantly affects posture recognition accuracy using machine learning. We validate our method's performance in five different real-world workplace environments and discuss training strategies for the machine learning models. Finally, we propose the first smart posture data-driven stretch recommendation system in alignment with physiotherapy standards. [ABSTRACT FROM AUTHOR]

In this paper, a pressure sensor based on a metal diaphragm and lever structure is designed, the sensing principle and mechanical structure of this sensor are analyzed and simulated, and its sensitization effectiveness and temperature compensation are verified. The maximum deflections of metal diaphragms of different sizes and materials were compared, and it was found that the square beryllium bronze diaphragm with a thickness of 1 mm and a side length of 20 mm had good elastic properties. The influence of the FBG in different positions of the lever on the center wavelength is analyzed. The sensitivity of the bare FBG is markedly improved under the influence of the two structures of the square elastic diaphragm and the lever, with a typical pressure sensitivity of 3.35 nm/MPa at 3 mm to the left of the lever center. The purpose of temperature compensation is achieved by adding another FBG that measures the temperature, and the sensing sensitivity can be tuned by adjusting the position of the FBG. It can meet the detection needs of a small range and high sensitivity. [ABSTRACT FROM AUTHOR]

A diaphragm-based hermetic optical fiber Fabry–Pérot (FP) cavity is proposed and demonstrated for pressure sensing. The FP cavity is hermetically sealed using one-step CO2 laser welding with a cavity length from 30 to 100 μm. A thin diaphragm is formed by polishing the hermetic FP cavity for pressure sensing. The fabricated FP cavity has a fringe contrast larger than 15 dB. The experimental results show that the fabricated device has a linear response to the change in pressure, with a sensitivity of −2.02 nm/MPa in the range of 0 to 4 MPa. The results demonstrate that the proposed fabrication technique can be used for fabricating optical fiber microcavities for sensing applications. [ABSTRACT FROM AUTHOR]

This paper discusses the fabrication and characterization of cyclic olefin copolymer (COC)-based pseudo-piezoelectric materials (piezoelectrets) with exceptionally high piezoelectric activity, and their potential use in sensing applications. Piezoelectrets that utilize a novel microhoneycomb structure to achieve high piezoelectric sensitivity are carefully engineered and fabricated at a low temperature using a supercritical CO2-assisted assembly. The quasistatic piezoelectric coefficient d33 of the material can reach up to 12,900 pCN−1 when charged at 8000 V. The materials also exhibit excellent thermal stability. The charge build-up in the materials and the actuation behavior of the materials are also investigated. Finally, applications of these materials in pressure sensing and mapping and in wearable sensing are demonstrated.

We theoretically investigate the defect mode transmittance of light waves in superconductor–semiconductor photonic crystals and its pressure-sensing dependence. The photonic crystal is composed of alternating superconducting and semiconducting slabs and a defect locates at the center of this structure. Two trapezoid waveguides are fixed at both sides of the crystal, which induces the hydrostatic pressure applied and beams transmitted simultaneously. The resonant wavelength variation in the defect mode is directly proportional to the pressure applied on the system in the near-IR region, which can be utilized for linear pressure sensors in the cryogenic environment. Pressure sensitivity reaches a high value of 2.6 nm/GPa, which is higher than that in the study based on the reflection spectra. The sensitivity coefficient may be modulated by the environment temperature as well. This study has potential regarding pressure-light-wave sensors.

Gel-based ionic conductors are promising candidates for flexible electronics, serving as stretchable sensors or electrodes. However, most of them suffer from a short operating life, low conductivity and rely on an external power supply, limiting their practical application. Herein, we report a stable organogel ionic conductor with high conductivity and self-powering ability. Briefly, lithium trifluoromethanesulfonate, as a conductive salt, provides high conductivity and the poly(1,1-difluoroethylene) layers, as a self-powering system, supply stable energy output under the influence of pressure. Moreover, the proposed conductors withstand long-term and multi-cycle durability tests. The prepared auxiliary training device can withstand the impact of a basketball and detect the impact force, showing potential in passive sensing during practical applications. [ABSTRACT FROM AUTHOR]

Numerous cuffs have been manufactured using different materials in which textile fabric is the main constituent. There are no specific guidelines for the selection of the cuff fabric and its design. In this investigation, five different types of cuffs (made of woven and non-woven fabrics) were selected, and their pressure distribution was noted while mimicking the process of blood pressure measurement. It was achieved by measuring pressure at the interface of the selected cuffs and a bare metal cylinder. I-scan, an interface pressure measurement system was employed to record the interface pressure profiles under the cuffs against 140 mmHg to 40 mmHg pressure inside the cuffs. The data obtained from the pressure sensing system was processed in MATLAB to examine pressure distribution at 96 points in detail. The results show that the cuffs registered non-uniform pressure distribution at the interface which is also non-identical among the selected cuffs. The pressure at the interface is found to be lower than the pressure inside the cuff, which shows that pressure attenuates as transfers to the surface of the object underneath it. The range of the pressure difference varies from 10 mmHg to 15 mmHg. This study indicates that the pressure distribution under a cuff depends on the constructing fabric and its properties. It is concluded that there is a need to select appropriate fabric with optimized properties for desired pressure distribution which may lead to accurate estimation of blood pressure. [ABSTRACT FROM AUTHOR]

A nanoengineered fabric capable of densely distributed pressure sensing is presented. Piezoresistive carbon nanotube-latex thin films were spray-coated and integrated with fabric to form robust, flexible, and deformable sensors. Spatial pressure sensing was achieved and validated experimentally using an electrical impedance tomography algorithm, which was able to estimate the resistivity distribution of the fabric and its changes due to applied pressure at different locations.

The authors propose a glove with pressure sensitive fingertips and muscle tension detection of the thumb to aid in the physiotherapy of infants, children and adults according to Vojta. The therapy has to be carried out at home by the parents of children with cerebral palsy, or other movement disturbances up to 4 times per day. Often, parents struggle to carry out the practices because of insecurities regarding the therapy’s proper application. The presented glove is tailored towards the specific needs of Vojta therapy, e.g. flexibility and small sensor size, and can help parents gather objective data on their therapy application at home. It has been tested in multiple therapy sessions on adult probands and seems to be a suitable tool to support parents and therapists in training alike. Additionally, the results of the accompanied therapy sessions provide arguments against what the critics have often cited about the painfulness of the therapy.

Electronic skins have been developed for sensing vertical pressure and tensile strain individually. Here, a stretchable, multifunctional, and 3D electronic skin (SMTE) is fabricated to imitate the squid's natural structure to achieve strain visualization and pressure sensing at the same time. The SMTE consists of an anisotropic and elastic light shutter to tune the natural color or fluorescence, which converts the in‐plane strain to the visual changes in color and intensity. The shutter also works as an elastic dielectric layer for vertical pressure sensing based on the principle of a single‐electrode triboelectric nanogenerator. The performance of the SMTE is demonstrated by integrating it on a model hand as a tactile sensor for touch, bending, and gesture interpretation, which has potential applications in human–machine interaction, soft robots, and artificial intelligence.

Soft robotic and medical devices will greatly benefit from stretchable and compliant pressure sensors that can detect deformation and contact forces for control and task safety. In addition to traditional 2D buckling via planar substrates, 3D buckling via curved substrates has emerged as an alternative approach to generate tunable and highly convoluted hierarchical wrinkle morphologies. Such wrinkles may provide advantages in pressure sensing, such as increased sensitivity, ultra-stretchability, and detecting changing curvatures. In this work, we fabricated stretchable sensors using wrinkled MXene electrodes obtained from 3D buckling. We then characterized the sensors’ performance in detecting strain, pressure, and vibrations. The fabricated wrinkled MXene electrode exhibited high stretchability of up to 250% and has a strain sensitivity of 0.1 between 0 and 80%. The fabricated bilayer MXene pressure sensor exhibited a pressure sensitivity of 0.935 kPa−1 and 0.188 kPa−1 at the lower (