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Current generation continuous flow assist devices to operate at a fixed speed, which limits preload response and exercise capacity in left ventricular assist device (LVAD) patients. A feedback control system was developed to automatically adjust pump speed based on direct measurements of ventricular loading using a custom cannula tip with an integrated pressure sensor and volume-sensing conductance electrodes. The input to the control system is the integral of the left ventricular (LV) pressure versus conductance loop (PGA) over each cardiac cycle. The feedback control system adjusts pump speed based on the difference between the measured PGA and the desired PGA. The control system and cannula tip were tested in acute ovine studies (n = 5) using the HeartMate II LVAD. The preload response of the control system was evaluated by partially occluding and releasing the inferior vena cava using a vessel loop snare. The cannula tip was integrated onto a custom centrifugal flow LVAD and tested in a 14-day bovine study. The control system adjusted pump support to maintain constant ventricular loading: pump speed increased (decreased) following an increase (decrease) in preload. This study demonstrated in vivo the Starling-like response of an automatic pump control system based on direct measurements of LV loading.

In this study, we propose a mechanical analysis for estimating the internal pressure of a finitely deformed spherical compartment from Lamb wave measurements. The proposed analysis produces a dispersion relation associating Lamb wave speed with pressure using limited material parameters (only a strain stiffening term). The analysis was validated on ultrasound bladder vibrometry (UBV) experiments collected from 9 ex vivo porcine bladders before and after formalin cross-linking. Estimated pressures were compared with pressures measured directly by a pressure transducer. The proposed analysis proved broadly effective at estimating pressure from UBV based Lamb wave without calibration as demonstrated by the observed concordance between estimated and measured pressures (Lin's CCC = 0.82 (0.66-0.91). Theoretical limitations and potential refinements to improve the accuracy and generality of the approach are discussed.

Stretchable, skin-conformal, and self-powered wearable pressure sensors have garnered significant attention for use in human joint bending motion monitoring. Here, a piezo-triboelectric pressure sensor (P-TPS) based on triboelectric nanogenerator and piezoelectric nanogenerator is demonstrated. The P-TPS can generate an enhanced electrical output by coupling the dual-mode triboelectrification and piezoelectric effect. The P-TPS shows high sensitivity (voltage = 0.3 V/kPa; current = 4.3 nA/kPa; pressure range = 0–200 kPa), high linearity, and good stability. Furthermore, it demonstrates a wide measurement range (0–800 kPa), table frequency response, and fast response time. Additionally, all components of the P-TPS are fabricated using flexible and stretchable materials, affording satisfactory stretchability and excellent skin conformality. Owing to their ability to self-power, they can be attached to the outside of joints to monitor human joint bending movements in real time. Hence, this study provides a novel method of using a stretchable and skin-conformal piezo-triboelectric nanogenerator with high electrical performance as a self-powered pressure sensor, which offers significant potential in personalized recognition, medical research, and human machine interface.

An experimental study of CO2 flows subjected to expanding conditions relevant to Mars entry is presented. A condition with a nominal velocity of 4.0 km/s was generated in the X2 expansion tunnel. ...

Electronic skins are artificial skin-type multifunctional sensors, which hold great potentials in intelligent robotics, limb prostheses and human health monitoring. However, it is a great challenge to independently and accurately read various physical signals without power supplies. Here, a self-powered flexible temperature-pressure bimodal sensor based on high-performance thermoelectric films and porous microconed conductive elastic materials is presented. Through introducing flexible heat-sink design and harvesting body heat energy, the thin-film thermoelectric device could not only precisely sense temperature signal but also drive the pressure sensor for detecting external tactile stimulus. The integration of Bi-Te based thermoelectric film with high stability in wide temperature range enables the sensor to sense the ambient temperature with high resolution (

With the fast development of electronic skin, there is a great demand for wearable sensing devices. Herein, a piezoresistive sensor has been fabricated comprising a conductive film of Polydimethylsiloxane (PDMS)-carbon nanotubes (CNTs) sandwiched by two protection films of PDMS. A simple and low-cost manufacturing method has been proposed to wrap CNTs inside the flexible PDMS to obtain a soft sensor with excellent conductivity, high sensitivity, and fast response to various pressures. Additionally, films with different percentages of CNTs were compared. The results show that the film with 7% CNTs has higher conductivity and sensitivity. Moreover, the surface morphologies and microstructures of the superior PDMS-CNTs film were studied by scanning electron microscope, and sensing properties of the pressure sensor were tested. Furthermore, applications of single sensor and sensor array were studied. The results exhibit that the as-prepared pressure sensor successfully detected different human motions and recognized Morse code and words, indicating that the portable sensor can be potentially applied in wide areas such as smart devices and flexible robotics.

Flexible piezoresistive pressure sensors based on a graphene-elastomer composite have gained popularity as electronic wearable sensors due to their simplicity and promising practical application in health monitoring and wearable devices. There is an urgent need to develop pressure sensors that are simplistic in design with good sensitivity and equally capable of production in large volumes. Studies have shown that implementing micro/nanostructures improves the sensitivity of graphene-elastomer pressure sensors. Therefore, in this paper, we fabricated thick nano wrinkles on a graphene-elastomer sandwich structure through a rapid thermal annealing procedure. The wrinkled structure was fabricated by rapid thermal annealing of spin-coated PEDOT:PSS (PH1000) on graphene-PDMS composite to facilitate the generation of wrinkles and optimize the sensitivity of our pressure sensor. We performed analyses on our pressure sensor under various compressive loading ranges. The pressure sensor detected pressure applied at these various ranges within a reasonable response time of 160ms and demonstrated excellent repeatability without hysteresis. In addition, we observed satisfactory sensitivity under tensile strain exhibiting high stretchability. The sensor displayed good sensitivity of 2.83 kPa-1 from compressive loading in the low-pressure range 0 Pa -490 Pa, and from 490 Pa-10 kPa the sensitivity was 0.12k Pa-1. The sensor demonstrated stretchability of up to 50% with a gauge factor of 20.1. We observed that it is highly responsive in the lower pressure range and capable of detecting subtle pressure. Furthermore, we demonstrated pressure detection in human motion monitoring. Overall, the pressure sensor displayed potential applications in human monitoring devices and wearable electronics.

Supercapacitors are widely used for powering flexible/wearable electronics owing to their excellent charge storage capabilities. In this study, MnO2 nanosheets were grown on the surface of graphene using a simple water bath method to prepare graphene/MnO2 composites for fabricating supercapacitors. In addition, two-dimensional black phosphorus was introduced as an additive into the electronic ink based on the as-prepared graphene/MnO2 composites. The characterization and electrochemical analyses results showed that adding black phosphorus considerably improved the capacitive performance of the material, yielding a high specific capacitance of 241.5 ​F ​g-1 at 0.1 ​A ​g-1 and an impressive rate capability improvement from 52.5% to 80.3%. Then the micro-supercapacitor having an area-specific capacitance of 20.15 ​mF ​cm-2 at a scanning rate of 2 ​mV ​s-1 was utilized to demonstrate the practical applicability of this material. To further evaluate the practical applicability of this micro-supercapacitor, the micro-supercapacitor was integrated with a flexible thin-film pressure sensor on paper and cloth through screen printing.

This study provides an experimental analysis of the throttling methods implemented using a throttleable injector that generates a thrust in the range 24–64% on a 50 N monopropellant thruster using ...

This paper presents the results of an in-depth study of the plasma-chemical etching (PCE) process of single-crystal silicon carbide (SiC) in SF6/O2 inductively coupled plasma (ICP). Using the method of optical emission spectroscopy (OES) we have examined the influence of RF power, bias voltage, pressure in the reaction chamber, and gas mixture composition on SiC PCE as well as the applicability of the OES technique for optimization and monitoring of SiC dry etching process in SF6/O2 ICP. An optimized PCE process for mass-manufacturing of SiC diaphragms of less than 20 μm thickness with an etch rate of more than 1.2 μm/min, and with an Rms of the etched surface of about 0.7 nm is developed. The influence of microtrenches on the electromechanical characteristics of the diaphragm as part of a capacitive pressure sensor is studied by means of computational simulation. An ideal diaphragm is compared with a real-process produced diaphragm with the microtrenching effect. It was shown that this effect has a great impact on the mechanical characteristics of the diaphragm. It is demonstrated that the von Mises stress at an applied pressure of 0.2 MPa for the real diaphragm is 183 MPa, while for the ideal diaphragm only 88 MPa.

Microsatellites have been widely applied in the fields of communication, remote sensing, navigation and science exploration due to its characteristics of low cost, flexible launch mode and short development period. However, conventional solid-propellant have difficulties in starting and interrupting combustion because combustion is autonomously sustained after ignition. Herein, we proposed a new type of solid-propellant named laser-controlled solid propellant, which is sensitive to laser irradiation and can be started or interrupted by switching on/off the continuous wave laser. To demonstrate the feasibility and investigate the controllable combustion behaviors under different laser on/off conditions, the combustion parameters including burning rate, ignition delay time and platform pressure were tested using pressure sensor, high-speed camera and thermographic camera. The results showed that the increase of laser-on or laser-off duration both will lead to the decrease of propellant combustion performance during re-ignition and re-combustion process. This is mainly attributed to the laser attenuation caused by the accumulation of combustion residue and the change of chamber ambient temperature. Simultaneously, the multiple ignition tests revealed that the increased chamber ambient temperature after combustion can make up for the energy loss of laser attenuation and expansion of chamber cavity. However, the laser-controlled combustion performance of solid propellant displayed a decrease trend with the addition of ignition times. Nevertheless, the results still exhibited good laser-controlled agility of laser-controlled solid propellant and manifested its inspiring potential in many aspects of space missions.

As an important medium of human-computer interaction, flexible tactile sensors have a vital influence on the intelligence and safety of a system by accurately identifying the contact position and force. For now, most of the existing flexible capacitive pressure sensors adopt an array structure, which still cannot meet the requirements including simple manufacturing, simple wiring, and low cost. This paper innovatively proposes a flexible array-less capacitive tactile sensor, a 30 mm × 30 mm sensor prototype, consisting of flexible electrodes and a dielectric layer of a polydimethylsiloxane (PDMS) and multiwalled carbon nanotube (MWCNT) composite. Under the action of a contact force, the contact area is deformed, resulting in a capacitance change in the flexible sensor. First, Poisson’s equation is used to determine the relationship between the electric potential and position. Then, elastic contact mechanics is adopted to describe the relationship between the electric charges and force. Finally, the contact position and force are recognized by measuring the change in capacitance in real time, based on the classical principle of capacitance. Simulation and experimental results verified the effectiveness of the proposed recognition method, showing that the recognition resolution of contact position can reach 500 μm × 100 μm, and the accuracy of contact force is 95.85%. Theoretically, the proposed flexible array-less sensor in this paper has infinite spatial resolution, and most importantly, it does not rely on complex manufacturing, redundant circuits, or sensor cell arrays. Therefore, it has broad application prospects in related fields such as electronic skin and wearable electronic devices.

With the rapid development of the flexible electronics field, flexible pressure sensors are widely used in wearable devices, medical monitoring and other fields. However, it is still a huge challenge to design a sensor with high sensitivity, low cost and a simple manufacturing process. In this paper, a resistive pressure sensor based on a composite conductive layer is developed. The polydimethylsiloxane (PDMS) is used as the matrix of the composite. The electrolyte fully absorbed by the super absorbent polymer (SAP+) and used as the conductive filler of the composite. The elastic polymer is used to replace the common rigid conductive fillers (such as carbon nanotubes, graphene, etc.), can be better combined with the matrix, greatly improving the stability and reducing the Young’s modulus of the sensor. After describing the working mechanism of the sensor, the influence of the composite conductive layer of different thicknesses and the content of SAP+ on the electrical output of the sensor is discussed. In addition, the sensor exhibits high sensitivity (0.062 kPa-1), a fast response time (0.136 s) and excellent cyclic loading/unloading stability (> 500 cycles).

We report a high yield fabrication process based on surface micromachining of sapphire substrates and plasma-deposited thin films for pressure sensors with extraordinarily high output swing relative to baseline and parasitic capacitance. This feature allows the use of massively parallel diaphragms arrays in a single sensor chip that is read out with a single interface circuit, providing a superior full-scale range and resolution in a small footprint. Five types of sensor chips are reported, incorporating: a) a single diaphragm (o100 μm diameter); b) 18 diaphragms in parallel (o100 μm diameter); c) 85 diaphragms (o56-o92 μm diameter); d) 8 diaphragms in parallel (o200 μm diameter); and e) 32 diaphragms in parallel (o110-o150 μm diameter). The respective maximum gauge pressures are 30 MPa, 30 MPa, 70 MPa, 70 kPa, and 110 kPa; the respective resolutions are 1.0 kPa, 0.2 kPa, 0.5 kPa, 5.7 Pa, and 2.6 Pa. Full-scale range is defined with the upper boundary as the applied pressure at which the incremental response falls below 30% of the incremental response at the lower boundary (which is approximated as atmospheric pressure). In two of these cases, varying diameters are used to reduce the inherent non-linearity of the sensor response over the full-scale pressure range. The 85-diaphragm sensor, intended for downhole pressure sensing, provides a capacitance response of 0.46 fF/kPa and 7.1 pF C0. The 32-diaphragm sensor, intended for lower operating pressures, provides capacitance response of 29 fF/kPa and 11.5 pF C0. The fabrication process, design features, and experimental results are presented.

Carbon nanotubes (CNTs) have broad application prospects in flexible pressure sensors because of their superior mechanical and electrical performance. However, the pressure sensitivity of a pure CN...

A novel flexible capacitive pressure sensor based on hybrid micro-structured (HM) polydimethylsiloxane (PDMS) dielectric layer was developed. The HM-PDMS with M-tooth structured patterns was fabricated using a laser engraved acrylic master mold. The top and bottom electrodes were fabricated by depositing silver (Ag) on flexible polyethylene terephthalate (PET) substrate using additive screen-printing process. The pressure sensor was assembled by sandwiching two HM-PDMS based dielectric layers between the top and bottom electrodes. The capability of the developed pressure sensor to detect a wide range of pressure was investigated by applying varying pressure from 0 to 1 kPa, 1 to 10 kPa, and 10 kPa to 40 kPa. A sensitivity of 51.36% kPa-1, 8.37% kPa-1, and 2.46% kPa-1 was obtained for the pressure ranges of 0 to 1 kPa, 1 to 10 kPa, and 10 to 40 kPa, respectively. The capacitive pressure sensor response, hysteresis, and repeatability of the fabricated pressure sensor is investigated and presented in this paper. To demonstrate the wide sensing range of the pressure sensor, the sensor was attached to face mask for breath monitoring applications that require low pressure sensing of ~20 Pa, and to the hand glove for fingertip pressure monitoring applications that require relatively high pressure sensing of ~3 kPa.

A distributed pressure sensor is proposed and designed for dynamic pressure measurement by using frequency-agile fast Brillouin optical time-domain analysis (BOTDA). A double coated single-mode fiber (SMF) is used as the sensing fiber because of its 1500- $\mu \text{m}$ thickness outer coating that can significantly improve the dependence of the Brillouin frequency shift on pressure. Then, the frequency-agile technique is used to generate frequency-agile pump pulse in BOTDA system so that a fast Brillouin gain spectrum distribution measurement can be achieved. An injection locked scheme is used as both optical filter and optical amplifier to improve the measurement accuracy. As a result, the static pressure sensitivity of the double coated fiber is −3.46 MHz/MPa with the pressure ranging from 0 to 30 MPa. Subsequently, a large dynamic range pressure measurement is performed with a sampling rate of 33.3 kHz and maximum sensing distance of 25 m. Furthermore, it is proved that the uncertainty of dynamic pressure measurement system is 0.03 MPa.

As a nano-scale composite functional material, the basic structure of the new magnetic fluid is to uniformly disperse the magnetic solid particles adsorbed with surfactants into the base liquid, thus forming a stable colloid system with high dispersion. Magnetic fluid can exist stably for a long time even under the action of gravity field, magnetic field and electric field without precipitation and separation. This kind of magnetic fluid has both magnetic and liquid fluidity under the action of magnetic field, so it has great potential for the application of magnetic fluid in the field of sensors. This paper mainly analyzes the research achievements of magnetic fluid in the neighborhood of micro-differential pressure sensor at home and abroad in recent years, and introduces the working principle and latest research progress of magnetic fluid sensor. Thus, making use of the special properties of magnetic fluid, it is applied to some problems in the field of micro-pressure difference sensor and the research direction of magnetic fluid micro-pressure difference sensor in the future.

Deformable 3D structures have emerged to revolutionize next-generation flexible electronics. In this study, a large out-of-plane deformable kirigami-based structure integrated with traditional functional materials has been successfully applied to wirelessly sense mechanical vibration and pressure. Unlike spiral inductor coils that lack mechanical stability, the inductor coils supported with polymer kirigami designs, comprising concentric circles with alternately connected hinges among the consecutive layers, offer exceptional mechanical stability. The wireless sensor shows a good linear response (Adj. R2 = 0.99) between the shift in resonant frequency as a function of extension. Moreover, the sensor device exhibits excellent cycling mechanical stability and minimal hysteresis, as confirmed by the experiments performed for over 5 d. An acceleration sensor (0-20 ms-2) with high linearity (Adj. R2 = 0.99) is introduced. Furthermore, a highly sensitive low-pressure sensor is demonstrated wirelessly in real time. Thus, the sensor can wirelessly monitor mechanical vibration and pressure. It can be applied for motion tracking, health monitoring, soft robotics, and deformation detection in battery-free deformable electronic devices.

Flexible wearable pressure sensors have attracted great interest from researchers in recent years because of their important applications in human-machine interaction, human behavior detection, medical diagnosis, and other fields. At present, integrating multiple functions such as pressure and temperature sensing and self-cleaning into a single material remains a challenging task. Here, by in situ reduction of graphene oxide (GO) grown on a sponge surface and deposition of polypyrrole (PPy) nanoparticles, we have built a highly sensitive, stable, and multifunctional rGO/PPy/poly(dimethylsiloxane) (PDMS) polyurethane (PU) sponge (GPPS) sensor for the detection of pressure, water level, and temperature. This multifunctional sensor shows excellent pressure-sensing performance, ultrasensitive loading sensing of a leaf (98 mg), and outstanding reproducibility over 5000 cycles. Due to the stability of the superhydrophobic surface water contact angle (WCA) = 153.3°, our sensor can work in an underwater environment, which can sense water levels from 1 cm (∼98 Pa) to 40 cm and also a variety of underwater behaviors (knock, ultrasonication, blow, etc.) with high stability. In addition, the sensor can be integrated into a circuit for the water level and pressure detection. The sensor can also be used as a smart underwater-temperature sensor; it shows a linear temperature coefficient of resistance (TCR) of 0.48% °C-1 in a temperature range of 35-80 °C. This multifunctional sensor shows potential application prospects in wearable electronic devices for sensing.

Monitoring biophysical signals such as body or organ movements and other physical phenomena is necessary for patient rehabilitation. However, stretchable flexible pressure sensors with high sensitivity and a broad range that can meet these requirements are still lacking. Herein, we successfully monitored various vital biophysical features and implemented in-sensor dynamic deep learning for knee rehabilitation using an ultrabroad linear range and high-sensitivity stretchable iontronic pressure sensor (SIPS). We optimized the topological structure and material composition of the electrode to build a fully stretching on-skin sensor. The high sensitivity (12.43 kPa−1), ultrabroad linear sensing range (1 MPa), high pressure resolution (6.4 Pa), long-term durability (no decay after 12000 cycles), and excellent stretchability (up to 20%) allow the sensor to maintain operating stability, even in emergency cases with a high sudden impact force (near 1 MPa) applied to the sensor. As a practical demonstration, the SIPS can positively track biophysical signals such as pulse waves, muscle movements, and plantar pressure. Importantly, with the help of a neuro-inspired fully convolutional network algorithm, the SIPS can accurately predict knee joint postures for better rehabilitation after orthopedic surgery. Our SIPS has potential as a promising candidate for wearable electronics and artificial intelligent medical engineering owing to its unique high signal-to-noise ratio and ultrabroad linear range. An ultrabroad-linear range (1 MPa) iontronic pressure sensor with superior sensitivity (12.43 kPa-1) and stretchability (up to 20%) was proposed for biophysical monitoring and deep learning-based knee-rehabilitation training.

Supersonic flow over a wall-mounted hemisphere was experimentally investigated to understand the shock-wave/boundary-layer interactions, flow separation, and other complex flow features associated ...

Optical fiber sensors have numerous advantages and are widely used in several fields. A typical optic fiber Fabry-Perot (FP) sensor is used to determine the pressure and temperature. To improve the sensitivity and overcome various limitations of pressure- and temperature-sensitive sensors, in this study, we demonstrate a micro-pressure FP sensor fabricated on an optical fiber through a chemical etching process. A graphene diaphragm was used as a pressure-sensitive membrane. The influence of FP cavity’s geometric parameters on the reflected signal was studied and simulated by following the optical transmission matrix theory. A finite element simulation of the model’s deflection behavior was carried out through ANSYS static mechanics, which verified the pressure-sensitive model’s accuracy. Experimental results show that the sensor exhibits high linearity and a sensitivity of 79.956 nm/kPa when the pressure ranges from 0 to 0.1 MPa. During pressure testing, a genetic algorithm-based wavelet neural network was used to compensate for temperature drifts in the optic fiber FP pressure sensors.

This paper describes the characterization and testing of a temperature-compensated optical fiber platform for silicon sensors. Our sensor platform consists of standard optical fiber hardware for optically-balanced and wavelength-multiplexed reflection measurements. We show that thermal effects in silicon sensors are significant for operational temperatures from 275-315 K but can be compensated using a collocated nano-fabricated temperature sensor. Our silicon temperature sensor is a $150~\mu \text{m}$ wide and $5~\mu \text{m}$ thick disk that is fabricated on the wafer-scale with a 3 mK/ $\sqrt {Hz}$ resolution and a 1.7 s thermal time constant in air. Our temperature-compensated platform has sufficient sensitivity and bandwidth to reduce thermal signals in silicon pressure sensors and microphones by more than an order of magnitude.

A sensitive pressure sensor based on ultralight and superelastic supercapacitive borophene-graphene aerogel as dielectric layer is reported. The borophene-graphene aerogel not only combines large specific surface area of reduced graphene oxide and high conductivity of borophene, but also exhibits rich porous structure. The strong synergy and intercalation between two different two-dimensional materials benefit electron transfer and electrolyte ion diffusion. On the one hand, the aerogel exhibits greater mass specific capacitance of 330 F g−1 than pure graphene aerogel. More importantly, serving as dielectric layer for pressure sensors with a symmetrical structure, the sensor represents ultra-high sensitivity (0.90 KPa−1) in the pressure range (

An optical fiber Mach-Zehnder interferometer based on an inner air-cavity with an open micro-channel structure is presented. The device is fabricated by using femtosecond laser to inscribe a cavity structure in the optical fiber core, followed by discharging the cavity area with a fusion splicer to form an inner air-cavity in the fiber core, and finally create an open micro-channel with the help of hydrofluoric acid corrosion. The fiber in-line interferometric device is miniature, robust, and stable in operation and exhibits a high pressure sensitivity of ~3351 pm/MPa, with an extremely low temperature cross-sensitivity of 2.58 kPa/°C.

Electronic skin (E-skin) based on tactile sensors has great significance in next-generation electronics such as biomedical application and artificial intelligence that requires interaction with humans. To mimic the properties of human skin, high flexibility, excellent sensing capability, and sufficient spatial resolution through high-level sensor integration are required. Here, we report a highly sensitive pressure sensor matrix based on a piezoresistive cellulose/single-walled carbon nanotube-entangled fiber network, which forms its own porous structure enabling a superior pressure sensor with a high sensitivity (9.097 kPa-1), a fast response speed (

Trapeziectomy is performed for trapeziometacarpal (TMC) arthritis but decreased lateral pinch strength is a major source of discomfort after the surgery. The magnitude of the decrease is unclear, however, and how the pressure changes in the TMC joint is unknown. To investigate this relationship, we designed a cadaveric study to measure TMC joint pressure using a lateral pinch model, and quantitatively evaluated the effect of trapeziectomy on the pressure measurements. For 10 cadaveric forearms, physiologic forces were applied across the thumb TMC joint by loading five tendons, thereby simulating lateral pinch. Using pressure sensors, we measured the lateral pinch pressure and TMC joint pressure, which averaged 10.1 (range, 4.2-16.2) kg/cm2 and 2.0 (range, 0.8-4.4) kg/cm2 , respectively. A significant correlation between the measurements was found, with an average ratio of 19% (range, 10%-27%). After trapeziectomy and interposition of the tendon ball using flexor carpi radialis, the pressure measurements were repeated under the same conditions. Significant changes were found, which averaged 5.1 (range, 1.7-10.7) kg/cm2 for lateral pinch pressure and 15.0 (range, 5.6-25.6) kg/cm2 for TMC joint pressure. In conclusion, TMC joint pressure could be measured as the ratio relative to lateral pinch pressure using a cadaveric model. After trapeziectomy, the lateral pinch strength decreased, whereas the TMC joint pressure increased.

A quartz resonant pressure sensor for ultra-high pressure measurement has been designed and verified. The pressure conversion unit of the sensor is composed of a pressure cylinder and a flexible lever, which can accurately and efficiently meet the role of converting and passing the ultra-high pressure to the resonant unit. The resonant unit of the sensor uses quartz DETF resonators and forms a differential output structure to meets the requirements of high precision and stability. The theory of the overall sensor design scheme is consistent with the simulation results, which verifies the feasibility of the design scheme. The experimental results show that in the pressure range of 120 Mpa, the sensitivity of the ultra-high pressure sensor is 27.3 Hz/Mpa, the linearity reaches 0.0112%, and the total accuracy is 0.0365%. The sensor can be used for high-precision and high-stability detection of ultra-high pressure, which is necessary in special fields such as deep-sea exploration.

Development of flexible, low cost, highly sensitive, and large-area compliance pressure sensors that can detect human physiological signals have become one of the vital component units for wearable electronics. Herein, a highly flexible and stretchable carbon black-porous polydimethylsiloxane-based pressure sensor has been successfully fabricated using a simple and effective fabrication technique with a sacrificial power template method. The pore size on the performance of pressure sensor is systematically investigated using KCl, NaCl, and sugar as powder templates to produce the porous PDMS. Notably, the KCl-templated PDMS pressure sensor exhibits a maximum pressure sensitivity (1.07 kPa−1 in 0–2 kPa), which is significantly higher than that of the NaCl-templated PDMS pressure sensor (0.86 kPa−1 in 0–2.5 kPa) and the sugar-templated PDMS pressure sensor (0.40 kPa−1 in 0–2.8 kPa). The KCl-templated PDMS pressure sensor has other advantages as well, including a fast response time of − 16 ms, a wide sensing range of 0–11,700 Pa, a low detection limit of − 2 mN, and a good reproducibility for over 3000 cycles. With these advantages, it is demonstrated that the pressure sensor can monitor minute mechanical events and human physiological signals, such as weak airflow blown, swallowing motion, finger touch, and pronunciation. Therefore, this new pressure sensor, which exhibit excellent comprehensive performance, will have wide application prospects in health monitoring and wearable devices.

In considering the critical role of crystal orientation and working temperature in shaping overall performance of piezoresistive pressure microsensors, this study investigates the effect of wafer orientation (i.e., crystal orientation) and working temperature on thermomechanical and fracture behaviour of a P-type silicon wafer used in pressure sensors. The study was carried out using analytical analysis, based on Kirchhoff–Love plate theory, and numerical analyses side by side with experimental investigations for validation and comparison purposes. The study addresses the following objectives: (1) to investigate the effects of working temperature, wafer positioning and crystal orientation on deflection and fracture behaviour of a silicon membrane; (2) to compare wafer deflections obtained experimentally to those obtained from simulations and numerical approaches; and (3) to determine the effect of maximum wafer deflection on crack initiation and fracture mode through the application of an experimental thermomechanical technique. An agreement between experimental and simulated deflection values of the Si wafer within a temperature range of 25–80 °C was concluded. Moreover, when working temperatures are below 100 °C, the fracture mode is highly brittle when a wafer is oriented at 0° and 45° with respect to [110] directions, whereas the wafer tends to render some ductility at temperatures above 120 °C. It was also found that at room temperature fracture occurs at a deflection of about 389 µm and 463 µm when the crystal is oriented at 45° and 0°, respectively.

All-paper sensors that are capable of free cutting and folding maximize the merits of papers, which fully utilize the unique potential of papers in cost effectiveness, flexibility, disposability, biodegradability, and a flexible design. However, most of the paper sensors have applied metals as the electrodes and polyimide/polydimethylsiloxane as the encapsulation/sensitive layers, limiting the advantages of the paper sensor. In this work, an all-paper, shape-designable, and reconfigurable capacitive pressure/proximity sensor is fabricated with multilayered tissue paper as the dielectric and polypyrrole printer paper as the electrode/encapsulation. Without the restriction of heterogeneous materials, the all-paper components enable the sensors' flexible shape design for freely cuttable and foldable 2D and 3D sensors including a 2D braille keyboard and even allow reconfiguration from a 3D box sensor to a 3D candy sensor. The all-paper sensor presents superior pressure-sensing performance (0.96 kPa-1 at

Ultrathin sensing devices utilizing piezoelectric materials have emerged as potential candidates to develop highly skin-conformable and energy-efficient continuous biosignal monitoring systems. However, biocompatible, cost-efficient, and simple fabrication processes still need to be investigated to enable wider adoption of such devices. This study proposes a simple two-step printing process for the fabrication of a piezoelectric biosignal sensor that utilizes readily available and biocompatible polymer-based materials for the substrate (i.e., Parylene-C), electroactive layer (i.e., poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)), and interdigitated electrodes (i.e., poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)). The proposed interdigitated electrode architecture improves upon the conventional metal–insulator–metal architecture by (1) increasing the thickness-normalized output voltage and (2) enabling the detection of bending orientation. The performance of the proposed sensor structure is demonstrated with the measurement of the arterial pulse waveform signal and limb movement detection. The presented results pave the way for cost-effective and continuous unobtrusive on-skin biosignal monitoring. publishedVersion

The increasing demand for flexible and wearable electronics has promoted the rapid development of the pressure sensors capable of monitoring diverse human movements and physiological signals. However, more and more research requires the pressure sensor to possess high sensing performance and desires the fabrication to exhibit the characteristics of low cost, large-scale production, high reproduction, even disposability. Here, we propose a full tissue-based capacitive pressure sensor with a sandwiched structure consisting of two MXene-coated tissue electrodes and a blank tissue dielectric layer. The tight contact and adequate adsorption of the MXene sheets with the cellulose fibers endow the electrode with uniform conductivity and high stability over a large area. In addition, the flexible sensor could be conveniently cut into any shape and size to meet the diverse application requirements. Thereby, the pressure sensor exhibits a sensitivity of 0.051 kPa–1 (

This paper presents an all-SiC fiber-optic Fabry-Perot (FP) pressure sensor based on the hydrophilic direct bonding technology for the applications in the harsh environment. The operating principle, fabrication, interface characteristics, and pressure response test of the proposed all-SiC pressure sensor are discussed. The FP cavity is formed by hermetically direct bonding of two-layer SiC wafers, including a thinned SiC diaphragm and a SiC wafer with an etched cavity. White light interference is used for the detection and demodulation of the sensor pressure signals. Experimental results demonstrate the sensing capabilities for the pressure range up to 800 kPa. The all-SiC structure without any intermediate layer can avoid the sensor failure caused by the thermal expansion coefficient mismatch and therefore has a great potential for pressure measurement in high temperature environments.

Due to the pressure gain combustion characteristics, the rotating detonation combustor (RDC) can enhance thermodynamic cycle efficiency. Therefore, the performance of gas-turbine engine can be further improved with this combustion technology. In the present study, the RDC operation performance with a turbine guide vane (TGV) is experimentally investigated. Hydrogen and air are used as propellants while hydrogen and air mass flow rate are about 16.1 g/s and 500 g/s and the equivalence ratio is about 1.0. A pre-detonator is used to ignite the mixture. High-frequency dynamic pressure transducers and silicon pressure sensors are employed to measure pressure oscillations and static pressure in the combustion chamber. The experimental results show that the steady propagation of rotating detonation wave (RDW) is observed in the combustion chamber and the mean propagation velocity is above 1650 m/s, reaching over 84% of theoretical Chapman-Jouguet detonation velocity. Clockwise and counterclockwise propagation directions of RDW are obtained. For clockwise propagation direction, the static pressure is about 15% higher in the combustor compared with counterclockwise propagation direction, but the RDW dominant frequency is lower. When the oblique shock wave propagates across the TGV, the pressure oscillations reduces significantly. In addition, as the detonation products flow through the TGV, the static pressure drops up to 32% and 43% for clockwise and counterclockwise propagation process respectively.

Monitoring of minor deformation in precision instruments is of great significance to guarantee the reliable operation. Polymer derived ceramic sensors with superior piezoresistive performance are promising. The traditional forming methods of the PDC sensor may cause the decline in mechanical properties. Thus, a silicon oxycarbide (SiOC) ceramic pressure sensor with diamond minimal surface structure were designed to improve the dimensional stability and ensure the uniform distribution of the stress. The percolation network comprising of electrically conductive free carbon was formed in the SiOC by the post heat treatment, which provided the structure superior piezoresistive property. The customized percolation network provided tunable sensing behavior and the resulting sensor had excellent accuracy and repeatability, possessing high sensitivity with the gauge factor of 297. More importantly, the sensor exhibited the high sensitivity with the small strains lower than 1.5%, indicating a reliable detection ability to the easily overlooked deformation. Additionally, the sensor had a high conductivity of 1.05 S/m and outstanding mechanical properties with the compressive strength and energy absorption of 15.11 MPa and 71.39 kJ•m−3. The printed sensor surmounts the limitations of current sensing materials, providing a promising way for the fabrication of high-performance and customized polymer derived ceramic pressure sensor.

Flexible microscopic pressure sensors are important to the emerging fields of intelligent robots and advanced healthcare. However, common microstructured pressure sensors often require sophisticated mould and/or material preparation, and yield limited pressure sensing performances. In this letter, we report a facile approach to design a scalable and stretchable mould-free sensitive layer with a unique hierarchical microstructure. Inspired by natural skin, a sensitive layer with interdigitated electrodes is utilized to constructed into resistive pressure sensors, which are able to robustly detect the pressure variations with high sensitivity in a wide dynamic range (about $33\,\,kPa^{-1}$ below 5 kPa, more than $0.6\,\,kPa^{-1}$ under 108 kPa), also deliver low hysteresis (within 8%), rapid response (less than 48 ms), and ultralow operation voltage ( $10~{\mu }V$ ). We illustrate that such self-patterned high-performance pressure sensors can be applied to convert the pressure stimulus into spike-like signals in both low- and medium-pressure regimes, and are being able to clearly reveal the details of human pulse wave.

At present, more and more flexible pressure sensors are used in wearable devices. The improvement of the adsorbability of nanomaterials on sponge flexible pressure sensors is an urgent problem to be solved. Here, using conductive carbon black with good dispersibility and small particle size as the conductive filler filled in the middle of the sponge can improve the absorbability of the sponge. A simple method of soaking a sponge with different thicknesses in conductive carbon black dispersion is used to obtain flexible pressure sensors based on conductive carbon black/sponge. We compare and analyze the differences in initial resistance and sensitivity of sponge pressure sensors with different thicknesses and select the sensor with higher sensitivity (0.194 kPa−1) for response time, recovery time, and stability tests. The sensor is used in the neck, wrist, knee, and other body parts for motion recognition. The two conductive carbon black/sponge sensors are placed orthogonally on the back to identify nod, tilt head, and placed on the elbow to test the angle of arm bending. Conductive carbon black/sponge flexible pressure sensor shows good application prospects in the wearable field.

In this letter, a novel integration of GaN chip with microdome-patterned polydimethylsiloxane (PDMS) film for pressure sensing is demonstrated. The compact $1\times {1}\times {0.2}$ mm3 GaN-on-sapphire chip consisting of light emitter and photodetector is formed through wafer-scale, high-throughput microfabrication processes. The integration of deformable dome-shaped PDMS enables the GaN chip to respond to the pressure variation effectively. The sensor exhibits a sensitivity of $0.989~\mu \text{A}$ /kPa for a wide pressure range of 0–50 kPa. In addition to the optical and electrical characteristics of the sensor, its prominent sensing performances of high repeatability and stability to dynamic pressure changes are studied through a range of experiments. The compact assembly scheme has advantages in manufacturing cost, compactness, and robustness, which is of great value for real-time pressure monitoring in a wide range of practical applications.

Pressure sensors based on discrete structure and multiple-contact mechanism (DSMM) have enabled high sensitivity and a wide range of nonlinear measurements in our previous work. In this work, we increased the density of the resistor array pixels and designed pixel patterns with varied separation distances to improve the sensing range and correct the sensing linearity, while maintaining the ultrahigh sensitivity of the DSMM pressure sensor. A refined calculation model was applied to simulate the multiple-contact mechanism and to optimize the sensing performance. The theoretical analysis and practical experiments agreed well. The ultrahigh sensitivity is 1.59/kPa for a small pressure range (

Conductive hydrogels are good candidates for flexible wearable sensors, which have received considerable attention for use in human-machine interfaces, human motion/health monitoring, and soft robots. However, these hydrogels often freeze at low temperatures and thus, exhibit low transparency, weak mechanical strength and stretchability, as well as poor adhesion strength. In this paper, conductive organohydrogels were prepared by thermal polymerization of acrylamide and N-(3-aminopropyl) methacrylamide in a glycerol-water binary solvent using NaCl as a conductive salt. Compared to other organohydrogels, our organohydrogels featured higher fracture stress (170 kPa) and greater stretchability (900%). The organohydrogels showed excellent antifreezing properties and high transparency (97%, at 400–800 nm wavelength) and presented outstanding adhesion strength to a variety of substrates. The conductive organohydrogels that were stored at −20°C for 24 h could still respond to both strain and pressure, showing a high sensitivity (gauge factor=2.73 under 100% strain), fast response time (0.4 s), and signal repeatability during multiple force cycles (∼100 cycles). Furthermore, the conductivity of cleaved antifreezing gels could be restored by contacting the broken surfaces together. Finally, we used our organohydrogels to monitor human tremors and bradykinesia in real-time within wired and wireless models, thus presenting a potential application for Parkinson’s disease diagnosis.

Wearable pressure sensors are highly desirable for monitoring human health and realizing a nice human-machine interaction. Herein, a chitosan/MXene/polyurethane-sponge/polyvinyl alcohol (CS/MXene/PU sponge/PVA)-based 3D pressure sensor is developed to simultaneously achieve wearability, washability, and high sensitivity in a wide region. In the force-sensitive layer of the sensor, MXene and CS are fully attached to the PU sponge to ensure that the composite sponge has remarkable conductivity and washability. Benefiting from the highly resistive PVA-nanowire spacer, the initial current of the sensor is reduced significantly so that the sensor exhibits extremely high sensitivity (84.9 kPa-1 for the less than 5 kPa region and 140.6 kPa-1 for the 5-22 kPa region). Moreover, the sensor has an excellent fast response time of 200 ms and a short recovery time of 30 ms, as well as non-attenuating durability over 5000 cycles. With the high sensitivity in a wide range, the sensor is capable of detecting multiple human and animal activities in real time, ranging from the large pressure of joint activities to a subtle pressure of pulse. Furthermore, the sensor also demonstrates the potential application in measuring pressure distribution. Overall, such a multifunctional pressure sensor can supply a new platform for the design and development of wearable health-monitoring equipment and an efficient human-machine interface.

Vacuum casting (VC) is a highly versatile manufacturing technique capable of producing parts in a wide range of polymers for end use plastic parts or prototypes. VC technology is ideally suited to low volume batch production compared with plastic injection molding since a silicone rubber mold (SRM) can be used to produce up to fifty to eighty parts. The main challenge of this method is that the both dimensional and form accuracies of the VC parts were affected by the fastening force of the SRM using tape due to the fastening force is inconsistent for different operators. In this study, an intelligent SRM clamping mechanism comprising a pressure sensor and Arduino pressure sensing module was developed for reducing the variations in both dimensional and form accuracies of the VC parts. It was found that the 14 kPa is the optimal clamping pressure. The angular deviation of the cuboid VC parts produced by the intelligent clamping mechanism falls within the range of one standard deviation (SD) to the average. The minimum zone circle deviation of the cylinder VC parts produced by the intelligent clamping mechanism falls within the range of − 1 to 2 SDs. In addition, the production cost of the SRM can further be reduced by about 23% using an intelligent clamping mechanism compared with that using the conventional method.