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Biomedical catheters are thin hollow tubes inserted into the human body to accurately measure various physiological parameters during invasive surgical procedures and diagnostic methods. Sensors realized using micro-/nano-electro-mechanical systems (MEMS/NEMS) technology are integrated with catheters to measure blood pressures, flows, pH- and glucose levels, and temperature. Of these physiological parameters, pressure sensing is of significant importance in identifying and treating various biomedical conditions. Piezoresistive technique is a widely investigated and preferred sensing mechanism to realize miniature sensors for its numerous advantages. In this paper, we critically review biomedical catheters as well as miniature piezoresistive pressure sensors developed for catheters. First, the evolution of catheters and their applications in measuring physiological parameters are discussed in detail. Next, the progress of piezoresistive pressure sensors developed for integration with catheters are described under three broad categories by considering various aspects such as diaphragm shape, material & size, piezoresistor type & material, readout type, fabrication processes, salient features of the device, and packaging techniques. A detailed section is devoted to alternative recent piezoresistive materials, including silicon nanowire (SNW), carbon nanotube (CNT), and Graphene. Finally, the process of catheterization and testing of biomedical catheters with integrated pressure sensors in the clinical environment are elaborated.

Since nonlinearity is critical to silicon piezoresistive pressure sensors, this paper combined theoretical analysis and simulation to study the effect of changing the longitudinal resistance (RL) and transverse resistance (RT) on the nonlinearity of pressure sensors. When initial longitudinal resistance (RL0) is larger than initial transverse resistance (RT0) and the difference is within a certain range, the nonlinearity of the pressure sensor can be effectively reduced. And based on this discovery, a method of an asymmetric Wheatstone bridge for optimizing nonlinearity of piezoresistive pressure sensors was proposed, which could reduce the nonlinearity from 10–3 to 10–6 order of magnitudes in the simulation.

Polymers are chemical structures that can be used for various applications. Depending on the structure of the polymer, they show various behaviour. While polymers are electrically insulator, they can conduct electricity by addition of conductive fillers. Sensors can be given as application examples of conductive polymer composites. In this work, conductive polymer composites were fabricated and their morphological, electrical and electro mechanical properties were characterized. According to outcomes, composites can be used as piezoresistive pressure sensors. In addition to that, magnitude and rate of the mechanical affect were found critical for the quality and sensitivity of the sensing behaviour.

The production of large wind turbine blades is a costly and time-consuming process. In order to obtain high-quality products and to avoid dry spots, it is necessary to monitor the resin flow during the resin infusion process. Using piezoresistive pressure sensors to perform in-situ measurement of the pressure gradient gives live information about the textile impregnation status during the manufacturing process and enables instant reaction if some anomalies are discovered. In this work, the effects of the used sensors on the static mechanical properties and the fatigue behaviour of the used glass fibre composites were investigated. The sensors were used during the manufacturing of large sandwich panels similar to that used in wind turbine blades. It was found, that the used sensors do not degrade the mechanical performance of the used materials and they are able to measure the pressure gradient during the manufacturing of wind turbine blades and to give information about the progress of the resin front.

Design and modeling of microelectromechanical system (MEMS)-based piezoresistive pressure sensor are main requirements to fabricate application-oriented pressure sensor devices for the industry, i.e., nuclear power plants, aerospace and avionics, oil and gas, Internet of Things, wearable electronics and consumer electronics. In this research work, analytical modeling is presented to estimate the overall sensitivity of the MEMS technology-based piezoresistive pressure sensor. The sensitivity of a piezoresistive pressure sensor is estimated using the thin plate theory and the theory of piezoresistivity in silicon. The mechanical responses of a thin plate in terms of deflection and induced stresses are presented and discussed. The effects of geometrical parameters on deflection and induced stresses are analyzed using a ratio of half-edge length with the thickness ( $$a/h$$ ) and a ratio of diaphragm edges ( $$a/b$$ ). These ratio parameters are responsible for the sensitivity of the piezoresistive pressure sensor. Moreover, a comparative assessment is presented for the current model with a model available in the literature. Further, calculations of average stresses are carried out for the piezoresistor geometry of a small rectangular area. Thereafter, a quantitative variation in the calculated sensitivity is presented based on calculation with maximum stress and average stress. The calculated difference in overall sensitivity is found to be 3%. However, a significant reduction in average stresses as compared to maximum induced stresses is obtained as 28% and 36% change for stress X and stress Y, respectively.

Polypyrrole (PPy) is a good candidate material for piezoresistive pressure sensors owing to its excellent electrical conductivity and good biocompatibility. However, it remains challenging to fabricate PPy-based flexible piezoresistive pressure sensors with high sensitivity because of the intrinsic rigidity and brittleness of the film composed of dense PPy particles. Here, a rational structure, that is, 3D-conductive and elastic topological film composed of coaxial nanofiber networks, is reported to dramatically improve the sensitivity of flexible PPy-based sensors. The film is prepared through surface modification of electrospun polyvinylidene fluoride (PVDF) nanofibers by polydopamine (PDA), in order to homogeneously deposit PPy particles on the nanofiber networks with strong interfacial adhesion (PVDF/PDA/PPy, PPP). This unique structure has a high surface area and abundant contact sites, leading to superb sensitivity against a subtle pressure. The as-developed piezoresistive pressure sensor delivers a low limit of detection (0.9 Pa), high sensitivity (139.9 kPa

The investigation of the pressure sensor chip’s design developed for operation in ultralow differential pressure ranges has been conducted. The optimum geometry of a diaphragm has been defined using available technological resources. The pressure sensor chip with an area of $6.15\times6.15$ mm has an average sensitivity S of 34.5 mV/ $\kappa $ Pa/V at nonlinearity 2K $_{NL} =0.81$ %FS and thermal hysteresis up to 0.6 %FS was created. Owing to the chip connection with stop elements, the burst pressure reaches $450~\kappa $ Pa. The developed pressure sensor can be used in medicine, automotive industry and highly specialized scientific developments.

This study considers existing metrological self-monitoring methods of sensors used in technological industries for measuring temperature and pressure. Furthermore, metrological self-monitoring methods of piezoresistive pressure sensors are analyzed. Then, a new metrological self-monitoring method is proposed on the basis of the supply voltage on the measuring diagonal of the bridge. The temperature of the piezoresistive bridge is determined using a semiconductor thermistor installed near the bridge. In this manner, the change in bridge resistance can be adjusted depending on the change in bridge temperature. With aging and exposure to external conditions, a change in the overall resistance of the piezoresistive bridge can be used to judge the error of the sensor. An experimental model of a piezoresistive pressure sensor is then developed. In the sample, the failure of the piezoresistive bridge is simulated by connecting an additional resistor in parallel with one of the arms of the bridge. The experimental studies show that the proposed technical method can assess the effect of changes in the total bridge resistance on the error of the sensor.

It is found that the strong light in the explosion field has great interference to the piezoresistive pressure sensor, then the shock wave data obtained by the sensor is distorted badly. To study the influence mechanism of the strong light on the piezoresistive pressure sensor, a strong light experimental platform is built. The positions of the sensor and the light source are adjusted, and the outputs of the piezoresistive pressure sensor are observed. Through microscopic simulation, the influence of different light intensities on the piezoresistive pressure sensor is analyzed. In order to reduce the influence of strong light on the performance of piezoresistive pressure sensor, we propose to add a reflective layer on the pressure surface of the sensor. The light reflection effects of different film thicknesses are analyzed through film simulation software. At the same time, the reflection effect is verified through experiments. To explain the effect of the reflective layer on the suppression of strong light, a simulation model is established, and the suppression effect of the reflective layer is verified.

Pressure sensitivity and wide range are two crucial features of flexible electromechanical sensors for applications in the next‐generation of intelligent electronics, such as wearable healthcare monitors and soft human–machine interfaces. Conventional pressure sensors have a narrow pressure range (

Flexible pressure sensors have attracted great attentions in recent years. In this work, an innovative piezoresistive pressure sensor was prepared using a flexible composite film by dip-coating a self-made PVA-CNTs (polyvinyl alcohol-carbon nanotubes) slurry on a layer of electrospun PVDF (polyvinylidene fluoride) fibrous network. A set of flexible sensor samples with different concentrations of PVA-CNTs slurry and different layers of electrospun PVDF network were investigated for sensing performances. The sensor made of double-layer PVDF network with 2 wt% CNTs of slurry was found to have good sensitivity, wide sensing range and little hysteresis effect of 0.0196 kPa−1, 0–40 kPa, and 13.1%, respectively. Furthermore, the sensor also presented good repeatability and stability over 80 compression cycles under a pressure of 35 kPa. Finger movement monitoring was also conducted by using the pressure sensor. Great comprehensive properties of the flexible piezoresistive pressure sensor indicated it a huge promising possibility of applications in human health detection and smart wears.

The investigation of the pressure sensor chip’s design developed for operation in ultralow differential pressure ranges has been conducted. The optimum geometry of a membrane has been defined using available technological resources. The pressure sensor chip with an area of 6.15х6.15 mm has an average sensitivity S of 34.5 mV/кPa/V at nonlinearity 2KNL = 0.81 %FS and thermal hysteresis up to 0.6 %FS was created. Owing to the chip connection with stop elements, the burst pressure reaches 450 кPa.

A mathematical model of an ultrahigh sensitivity piezoresistive chip of a pressure sensor with a range from -0.5 to 0.5 kPa has been developed. The optimum geometrical dimensions of a specific silicon membrane with a combination of rigid islands to ensure a trade-off relationship between sensitivity (Ssamples = 34.5 mV/kPa/V) and nonlinearity (2KNL samples = 0.81 %FS) have been determined. The paper also studies the range of the membrane deflection and makes recommendations on position of stops limiting diaphragm deflection in both directions; the stops allow for increasing burst pressure Pburst up to 450 кPa. The simulated data has been related to that of experimental samples and their comparative analysis showed the relevance of the mathematical model (estimated sensitivity and nonlinearity errors calculated on the basis of average values are 1.5% and 19%, respectively).

We demonstrate a simple, nonlithographic method for fabricating piezoresistive pressure sensors with a broad range of working pressures and low detection limit. Our wearable pressure sensor is fabr...

Wide band gap materials such as silicon carbide and diamond are considered more suitable compared to silicon for the fabrication of piezoresistive pressure sensors for operation at high tem...

Flexible pressure sensors are increasingly popular because of their extensive applications in smart textile and flexible robotics. Inspired by the composite hierarchical structure of conventional p...

Flexible piezoresistive pressure sensors featuring high sensitivity, wide operating pressure range, and short response time are required urgently due to the rapid development of smart devices and artificial intelligence. Herein, a high-performance flexible piezoresistive pressure sensor based on naturally formed hierarchical flower-shaped SnSe2 nanoplates and conical frustum-like structured polydimethylsiloxane (PDMS) is demonstrated. The micropatterned PDMS/Au and SnSe2 nanoplates/Au interdigital electrodes are exploited as the top and down part of the sensor, respectively. Benefiting from abundant contact sites and sufficient roughness provided by the SnSe2 nanoplates, the proposed sensing devices exhibit significantly enhanced sensitivity as high as 433.22 kPa–1 when compared with conventional configuration (planar Au film as the bottom interdigital electrodes). The resulting pressure sensor (PDMS/Au/Au/SnSe2) also presents wide operating pressure range (0–38.4 kPa), lower limit of detection (∼0.82 Pa), fast response time (∼90 μs), and long-term cycle stability (>4000 cycles). Therefore, it shows a great potential in various applications, such as the detection of the magnitude and distribution of the loaded pressure, as well as the monitoring of the human physiological signals. Ministry of Education (MOE) Nanyang Technological University Accepted version This work was partially supported by the Shenzhen Basic Research Grant (JCYJ20150925163313898, JCYJ20170413153246713, and JCYJ20180507182431967) and the National Nature Science Foundation of China (11804354, 61574157, and 61774164). The authors are also grateful for the support of the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2015-T2-1-066 and MOE2015-T2-2-010), Singapore Ministry of Education Academic Research Fund Tier 1 (RG85/16), and Nanyang Technological University (Start-up grant M4081515 to L.W.).

The effects of temperature on the output performance of piezoresistive pressure sensors are studied in this paper. The influences of the environmental temperature, the residual stress due to the fabrication process, and the residual stress due to the packaging on the piezoresistive coefficient and resistance are theoretically investigated. The simulation results are obtained via finite element analysis through ANSYS. The results of experimental studies performed on piezoresistive pressure sensors fabricated using MEMS techniques are reported to verify the simulation results. The output characteristics of piezoresistive pressure sensors are shown to be substantially affected by not only the environmental temperature but also the residual stresses from the fabrication and packing processes.

To investigate the performance of diamond based piezoresistive pressure sensors, we have carried out a simulation study for obtaining an estimate of the pressure response. The sensor comprised of a thin diaphragm of diamond as a primary sensing element and boron doped diamond piezoresistors as transduction elements. The diaphragm geometry was optimized to 750 μm × 750 μm with 35 μm diaphragm thickness for a pressure range up to 40 MPa. Subsequently, the placement of diamond piezoresistors on the top of the thin diaphragm was optimized to get the best sensitivity. Since diamond has a higher piezoresistive coefficient in the longitudinal direction, a configuration of two longitudinal piezoresistors near to diaphragm edge and the other two transverse piezoresistors near to the diaphragm centre was used for the placement of piezoresistors. The voltage response of the piezoresistive pressure sensor was estimated using simulations. A sensitivity of 0.27 mV/V/MPa was obtained for the optimized sensor parameters.

This paper first reports a new peninsula structure diaphragm (NPSD) piezoresistive pressure sensor, which has high sensitivity and linearity at the same time. By creating stress concentration areas and increasing the stiffness of the film, within the pressure range of 0–5 kPa, the sensitivity of the sensor reaches 22.7 mV/kPa while the nonlinearity is reduced to 0.11% FSO (full-scale output). Compared with our previous work, the sensitivity is increased by 23.4% while the nonlinearity is reduced by 69%. When the ambient temperature rises to 60°C, the sensor still has a high sensitivity of 21.5 mV/kPa.

Purpose: Micro Electronic Mechanical System (MEMS) based pressure sensors have found their use in multiple applications lately in the field of healthcare, automotive etc. These sensors however face a trade-off between sensitivity and linearity which limits sensor performance. The proposed design aims to achieve an enhanced sensor performance by alleviating the sensitivity and linearity trade-off.Methods: Novel structures such as annular grooves and center mass have been introduced for providing better sensor performance along with membrane dimension optimization. Annular grooves generate Stress Concentrated Regions (SCRs) on membrane surface on application of external pressure which enhances sensor sensitivity while center mass provides partial stiffening of the membrane and hence reduces non-linearity.Results: The proposed sensor achieves a low non-linearity error of 0.15% FSS with a well-balanced sensitivity of 28.0 mV/V/psi. Conclusion: The proposed novel sensor structure achieves a relatively better performance in comparison to conventional membrane variants. With a high sensitivity and appreciable linearity, the novel structure proves to be ideal for low pressure measurements in the range (0-5)KPa.

In this work, piezoresistive properties of graphene-multiwalled carbon nanotubes (MWCNTs) composites are investigated, characterized, and compared. Sandwich-type composite piezoresistive pressure-sensitive sensors (Ag/Graphene-MWCNT/Ag) with the same diameters, but different fabrication pressures and thicknesses were fabricated using the mortar and pestle/hydraulic press technique. To produce low-electrical-resistance contacts, both sides of the composite sensors were painted with silver (Ag) paste. All the sensors showed reductions in the direct current (DC) resistance ‘R’ with an increment in external uniaxial applied pressure. However, it was observed that higher fabrication pressure led to a lower resistance value of the composite, while the thicker samples give lower electrical conductivity and higher resistance than the thinner samples. The experimental data for all composite pressure sensors were in excellent agreement with the simulated results.

The pressure sensor technology has grown to a large market since its discovery. These sensors are widely used in all spheres ranging from commercial, industrial, biomedical and even to military applications. This study tends to provide a review of the micro electro mechanical systems (M EMS) Piezoresistive Pressure Sensor Technology. This study includes the basic engineering involved in these sensors, important terms and the performance characteristics. The aim is to present the detailed research in a concise yet precise form.

High hardness and corrosion resistance of SiC (silicon carbide) bulk materials have always been a difficult problem in the processing of an all-SiC piezoresistive pressure sensor. In this work, we demonstrated a SiC sealing cavity structure utilizing SiC shallow plasma-etched process (&le, 20 &mu, m) and SiC&ndash, SiC room temperature bonding technology. The SiC bonding interface was closely connected, and its average tensile strength could reach 6.71 MPa. In addition, through a rapid thermal annealing (RTA) experiment of 1 min and 10 mins in N2 atmosphere of 1000 &deg, C, it was found that Si, C and O elements at the bonding interface were diffused, while the width of the intermediate interface layer was narrowed, and the tensile strength could remain stable. This SiC sealing cavity structure has important application value in the realization of an all-SiC piezoresistive pressure sensor.

Fabricating flexible pressure sensors with high sensitivity in a broad pressure range is still a challenge. Herein, a flexible pressure sensor with engineered microstructures on polydimethylsiloxane (PDMS) film is designed. The high performance of the sensor derives from its unique pyramid‐wall‐grid microstructure (PWGM). A square array of dome‐topped pyramids and crossed strengthening walls on the film forms a multiheight hierarchical microstructure. Two pieces of PWGM flexible PDMS film, stacked face‐to‐face, form a piezoresistive sensor endowed with ultrahigh sensitivity across a very broad pressure range. The sensitivity of the device is as high as 383 665.9 and 269 662.9 kPa−1 in the pressure ranges 0–1.6 and 1.6–6 kPa, respectively. In the higher pressure range of 6.1–11 kPa, the sensitivity is 48 689.1 kPa−1, and even in the very high pressure range of 11–56 kPa, it stays at 1266.8 kPa−1. The pressure sensor possesses excellent bending and torsional strain detection properties, is mechanically durable, and has potential applications in wearable biosensing for healthcare. In addition, 2 × 2 and 4 × 4 sensor arrays are prepared and characterized, suggesting the possibility of manufacturing a flexible tactile sensor., A flexible piezoresistive pressure sensor with hierarchical microstructures on its interlocked polydimethylsiloxane sensing films is fabricated by using a specially designed silicon template with the unique pyramid‐wall grid microstructures of different height and a four‐step mold‐casting process. The sensor has ultrahigh sensitivity in a very wide pressure range, yielding better performance than most flexible pressure sensor in literature.

Flexible piezoresistive pressure sensors obtain global research interest owing to their potential applications in healthcare, human–robot interaction, and artificial nerves. However, an additional power supply is usually required to drive the sensors, which results in increased complexity of the pressure sensing system. Despite the great efforts in pursuing self-powered pressure sensors, most of the self-powered devices can merely detect the dynamic pressure and the reliable static pressure detection is still challenging. With the help of redox-induced electricity, a bioinspired graphite/polydimethylsiloxane piezoresistive composite film acting both as the cathode and pressure sensing layer, a neoteric electronic skin sensor is presented here to detect not only the dynamic forces but also the static forces without an external power supply. Additionally, the sensor exhibits a fascinating pressure sensitivity of ∼103 kPa–1 over a broad sensing range from 0.02 to 30 kPa. Benefiting from the advanced performance of the device, various potential applications including arterial pulse monitoring, human motion detecting, and Morse code generation are successfully demonstrated. This new strategy could pave a way for the development of next-generation self-powered wearable devices.

A measurement approach of resistive sensor arrays has posed more obstacles than in single point resistive sensors. The effect of a crosstalk current in the array is the main factor that results in an inaccurate resistance scanning. In the application of pressure sensors, the presence of crosstalk current will cause ghost images on the area where no actual force is exerted onto the sensor array. In this paper, the enhanced measurement circuit has been specifically designed based on the zero potential circuit method to overcome the crosstalk error for improved accuracy. PSPICE simulation results on the 5×5 resistive array showed improved accuracy compared to the previous voltage dividing measurement approach, with the error reducing from 12.987% to 1.191%.

Compressible and ultralight all-carbon materials are promising candidates for piezoresistive pressure sensors. Although several fabrication methods have been developed, the required elasticity and fatigue resistance of all-carbon materials are yet to be satisfied as a result of energy loss and structure-derived fatigue failure. Herein, we present a two-stage solvothermal freeze-casting approach to fabricate all-carbon aerogel [modified graphene aerogel (MGA)] with a multi-arched structure, which is enabled by the in-depth solvothermal reduction of graphene oxide and unidirectional ice-crystal growth. MGA exhibits supercompressibility and superelasticity, which can resist an extreme compressive strain of 99% and maintain 93.4% height retention after 100 000 cycles at the strain of 80%. Rebound experiments reveal that MGA can rebound the ball (367 times heavier than the aerogel) in 0.02 s with a very fast recovery speed (∼615 mm s

The results of the influence of the diaphragm shape of a piezoresistive pressure sensor on its parameters are determined in this article. Square, rectangular and round diaphragms made of monocrystalline silicon were studied. With the help of the ANSYS program, the simulation was performed, the parameters - deformations and mechanical stresses arising in diaphragms were calculated and which turned out to be different for diaphragms of different shapes. The results are analyzed; recommendations on the choice of diaphragm shape in sensors are given.

Demand of MEMS sensor is increasing due to its applicability in various fields such as in automobile and industrial applications. Save driving is very necessary which can be properly accomplish by usage of flexible MEMS devices which can monitor different parameters such as tyre pressure, speed etc. Tyre pressure monitoring system consists of flexible MEMS pressure sensor, which provide low power consumption and temperature compatibility by proper selection of the sensor material. In this paper, modelling of graphene based flexible piezoresistive pressure sensor has been carried out for monitoring of the tyre pressure. Graphene is used as a substrate material, which makes the flexible device that can be implanted easily in the tyre. Graphene is also used as the sensing material for piezoresistors. Results indicate that sensitivity of 0.63 mV/kPa is achieved at room temperature.

This paper presents the design methodology and fabrication process of a novel piezoresistive pressure sensor with a combined cross-beam membrane and peninsula (CBMP) diaphragm structure for micropressure measurements. The sensor is then analyzed through various experiments. The sensor is primarily designed based on the optimized sensitivity, and a finite-element method is used to predict the stresses that are induced in the piezoresistors and the deflection of the membrane under different pressures. Compared to other traditional diaphragm types, a significant increase in sensitivity can be achieved by the proposed sensor, and the membrane deflection and nonlinearity error considerably decrease. The sensor fabrication process is performed on an n-type single-crystal silicon wafer, and photolithography is used with five masks to fabricate the sensing elements. Additionally, piezoresistors are formed by boron implantation. The experimental results indicate that the fabricated sensor with the CBMP membrane yields a high sensitivity of 25.7 mV/kPa and a low nonlinearity of −0.28% full-scale span for a pressure range of 0–5 kPa at room temperature.

High-sensitivity pressure sensors are crucial for the ultrasensitive touch technology and E-skin, especially at the tiny-pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to 200 kPa–1 and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa–1 using short-channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 μs), excellent...

This paper reported novel high sensitivity and linear 0-1MPa piezoresistive pressure sensor for environmental applications. The proposed work as two different structures of membrane (square and rectangular) having the similar surface area and thickness has been studied. The design and analyzed pressure sensor parameters such as stress, deflection and sensitivity are obtained by using INTELLISUITE 8.8v. The simulated sensor showed a sensitivity of 6.8×10-12 for 7µm thickness, 18.5×10-12 for 5µm thickness and 84.2×10-12 for 3µm thicknessof square membrane is prepared through the finite element tool. This deflection change providesthe validate of the pressure in that atmosphere. Finally, we observed that the best deflection obtained from square membrane and maximum stress output reactions are obtained from the rectangular membrane with the pressure range from 0.1 MPa to 1MPa and also maximum deformation of 84 μm for 3 µm thickness, 18.55µm for 5µm thickness and 6.9µm for 7µm thickness. The effect of these studies can be used to improve the sensitivity of these devices.

Hydrogel-based sensors using the force compensation method show a strongly decreased dynamic drift and a much shorter response time. The sensor setup using a piezoresistive pressure sensor to measure and control the pressure equilibrium becomes complex since an external force, e.g., caused by compressed air or a second hydrogel, must be applied from the opposite side. In addition, the swelling pressure of the hydrogel can lead to internal damage of the polymer chains when exposed to high force impacts. A particularly tailored bisensitive hydrogel was designed and synthesized to address these problems. It simultaneously fulfills the functions of a transducer (for sensing) and of an actuator (for volume compensation). The force compensation thus occurs internally within one single hydrogel, and an external force is no longer required. In the particular case considered in this article, the hydrogel was designed to be sensitive to salt concentration c NaCl and to temperature ϑ. As a result, it was possible to quasi-statically maintain the volume at a constant value for different values of c NaCl by applying a corresponding temperature ϑ.

The theoretical aspects of a new type of piezo-resistive pressure sensors for environments with rapidly changing temperatures are presented. The idea is that the sensor has two identical diaphragms which have different coefficients of linear thermal expansion. Therefore, when measuring pressure in environments with variable temperature, the diaphragms will have different deflection. This difference can be used to make appropriate correction of the sensor output signal and, thus, to increase accuracy of measurement. Since physical principles of sensors operation enable fast correction of the output signal, the sensor can be used in environments with rapidly changing temperature, which is its essential advantage. The paper presents practical implementation of the proposed theoretical aspects and the results of testing the developed sensor.

This paper presented a novel 0-3 kPa piezoresistive pressure sensor with high sensitivity and linearity. A shuriken-structured diaphragm (SSD) is designed for the first time to solve the conflict between the sensitivity and linearity for piezoresistive pressure sensors. A trade-off between the stress on the diaphragm edge and the deflection of the diaphragm was achieved by this SSD design according to the numerical simulation. The effects of the glass substrate and the passivation films on the sensing performance were also studied numerically and experimentally. The experimental results indicated the present pressure sensor had a sensitivity of 4.72 mV/kPa/V and a linearity of 0.18 %FSO (full scale output) in the pressure range of 0-3 kPa, which were 28.3% and 50% better than the previous works.

The paper describes the fabrication of a silicon carbide piezoresistive pressure sensors intended for operating temperatures of up to 600°C. The different fabrication aspects, such as the metallization scheme, the etching of a 300μm deep cavity, and the bonding to a silicon carbide back plate are discussed in detail.

Three-dimensional (3D) graphene based wearable piezoresistive sensors are considered as promising flexible sensors due to their facile preparation, simple read-out mechanism, low power consumption and convenient signal acquisition. After nearly two decades of rapid development, 3D graphene based piezoresistive sensors have shown excellent application potential in human motion detection, heath monitoring, electronic skin, etc., which are envisioned as the critical technologies in future artificial intelligence system. In this review, the rapid development of 3D graphene based piezoresistive sensors are focused and analyzed. Various preparation methods of graphene and the complex fabrication process of multilevel 3D graphene structure are summarized, followed by the analyzing of different working mechanisms of 3D graphene-based piezoresistive sensors, which are illustrated by examples. The challenges and prospects of 3D graphene-based piezoresistive pressure sensors are discussed.