Display omitted
Flexible pressure sensors with high sensitivity, high flexibility, lightness and easy integration have been extensively researched in the fields of electronic skin, wearable devices, ...medical diagnosis, physical health detection and artificial intelligence. This review summarizes the latest research progress of piezoresistive pressure sensors, capacitive pressure sensors, and piezoelectric pressure sensors. In addition, high-performance flexible pressure sensors designed for different application requirements such as self-powered pressure sensors, multifunctional pressure sensors, and self-healing pressure sensors are also discussed. After a comprehensive description of the latest flexible pressure sensors, we discussed the current challenges and potential prospects of flexible pressure sensors. Exploring new sensing mechanisms, seeking new functional materials, and developing novel integrated technologies for flexible devices will be the key direction in the sensor field in the future.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, and more. In particular, liquid‐metal‐based sensors are especially promising as they ...can undergo strains of over 200% without failure. However, current liquid‐metal‐based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart‐rate monitoring, which require a much lower pressure detection resolution. In this paper, a microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width × 70 µm height) capable of resolving sub‐50 Pa changes in pressure with sub‐100 Pa detection limits and a response time of 90 ms is demonstrated. An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of a 0.0835 kPa−1 change in output voltage. The Wheatstone bridge also provides temperature self‐compensation, allowing for operation in the range of 20–50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real‐time pulse monitoring and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated.
A flexible microfluidic diaphragm pressure sensor using liquid‐metal microchannels is presented. The sensor is capable of detecting sub‐100 Pa pressures with sub‐50 Pa resolution. As a proof of concept, both heart‐rate monitoring and tactile pressure mapping of a glove with multiple embedded sensors are demonstrated.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Three types of piezoresistive pressure sensors were designed and fabricated using different process technologies incorporating standard diffused piezoresistors, and oxide isolated polysilicon or ...single crystal silicon piezoresistors. The performance of these sensors up to an elevated temperature of 200°C and pressure of 140 bar was investigated by measuring the variation of sensitivity, offset voltage and hysteresis. At room temperature, the diffused piezoresistor based pressure sensor demonstrated sensitivity of 0.147 mV/V/bar and it was observed to operate up to the maximum temperature of 100 °C. The oxide isolated single crystal silicon piezoresistor and polysilicon piezoresistor based pressure sensors showed sensitivities of 0.211 mV/V/bar and 0.308 mV/V/bar respectively at room temperatures. These sensors could be operated up to the measured temperature of 200 °C without any failure. All types of sensors showed decreased sensitivities with temperature. With respect to the sensitivity at room temperature, the sensor with diffused piezoresistors exhibited 13% decrease of sensitivity at 100 °C. For oxide isolated single crystal silicon or poly silicon piezoresistors, the decrease in the sensitivity at 200 °C was 19.5% and 9.0% respectively y. At elevated temperatures of 200 °C, the sensors with oxide isolated polysilicon piezoresistors demonstrated the best performance in terms of lowest decrease of sensitivity, and variation of offset voltage and hysteresis.
A new type of flexible pressure sensor with air gap has been designed based on polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). During fabrication, the interdigitated Ag electrode was ...fabricated on the bottom PDMS layer by doctor blading and AgNWs were embedded in the top PDMS layer, with a naturally formed air gap between the AgNW layer and the interdigitated electrodes. The thus-formed air gap was controlled by the number of AgNW layers and played an important role in enhancing sensitivity by decreasing the off current in the absence of pressure. The maximum sensitivity of 16.1 kPa−1 was obtained via optimization of the air gap thickness, the AgNW sensing area, and the channel length of the electrodes. The stability of the sensors was confirmed by durability, repeatability, bending, and hysteresis tests. The pressure sensor based on the highly sensitive AgNW network could provide a great opportunity for measuring various types of forces and displacements in wearable devices.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Polymer nanofibers are widely adopted in energy harvesting and pressure sensing applications owing to the large contact area and inherent compressibility. Herein, a high‐performance triboelectric ...nanogenerator (TENG) based on 2D siloxene‐polyvinylidene fluoride (S‐PVDF) composite nanofibrous membrane is newly evaluated. Through proper ratio optimization and facile electrospinning, the fabricated membrane shows significant improvement in dielectric property, electronegativity, and compressibility. The TENG comprising S‐PVDF membrane and Nylon 6/6 can deliver an excellent power density of 13.25 W m−2 (f ≈ 5 Hz) and easily operates low‐power electronics and Internet of things (IoTs). In addition, the excellent compressibility of membrane extends its applicability to self‐powered simultaneous detection of dynamic and static pressure, which is investigated by developing a hybrid pressure sensor (HPS) through effective integration of TENG and a capacitive pressure sensor. The HPS shows an excellent dynamic (12.062 V kPa−1 at (<3 kPa) and 2.58 V kPa−1 at (3–25 kPa)) and static (25.07 mV kPa−1 at (<3 kPa) and 5.96 mV kPa−1 at (3–25 kPa)) pressure sensitivities, respectively. Furthermore, a 2 × 2 HPS array tested and analyzed for multiple users using artificial intelligence significantly improves the accuracy (98%). Remarkable energy harvesting performance and greater accuracy of the HPS manifests better preferences for future self‐powered IoT and smart tactile‐based user authentication systems.
Herein, a high‐performance triboelectric nanogenerator based on siloxene‐polyvinylidene fluoride (S‐PVDF) composite nanofibrous membrane is demonstrated. Furthermore, by integrating a highly sensitive capacitive pressure sensor, a self‐powered hybrid sensor array that simultaneously measures static and dynamic pressure is presented. Excellent triboelectric performance and greater sensing accuracy highlight its usefulness in future self‐powered electronics and authentication platforms.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Wearable blood‐pressure sensors have recently attracted attention as healthcare devices for continuous non‐invasive arterial pressure (CNAP) monitoring. However, the accuracy of wearable ...blood‐pressure (BP) monitoring devices has been controversial due to the low signal quality of sensors, the absence of an accurate transfer function to convert the sensor signals into BP values, and the lack of clinical validation regarding measurement precision. Here, a wearable piezoelectric blood‐pressure sensor (WPBPS) is reported, which achieves a high normalized sensitivity (0.062 kPa−1), and fast response time (23 ms) for CNAP monitoring. The transfer function of a linear regression model is designed, offering a simple solution to convert the flexible piezoelectric sensor signals into BP values. In order to verify the measurement accuracy of WPBPS, clinical trials are performed on 35 subjects aged from 20 to 80 s after screening. The mean difference between the WPBPS and a commercial sphygmomanometer of 175 BP data pairs is −0.89 ± 6.19 and −0.32 ± 5.28 mmHg for systolic blood pressure (SBP) and diastolic blood pressure (DBP), respectively. By building a WPBPS‐embedded wristwatch, the potentially promising use of a convenient, portable, continuous BP monitoring system for cardiovascular disease diagnosis is demonstrated.
A wearable piezoelectric blood‐pressure sensor (WPBPS) using an extremely sensitive flexible piezoelectric sensor is demonstrated for continuous and non‐invasive arterial pressure (CNAP) monitoring. Its transfer function is designed by a linear regression model, offering a simple solution to convert the sensor signals into BP values. The high accuracy of WPBPS is confirmed through clinical validation with an oscillometric sphygmomanometer as a reference.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In this paper, three methods to improve the sensitivity of flexible capacitive pressure sensors are mainly reviewed, including (1) constructing microstructure of the dielectrics or electrodes, (2) ...adding conductive fillers to polymer elastomer to generate a composite dielectric, (3) introducing micro-holes into the dielectric layer.
Display omitted
•The main factors affecting the capacitance are dielectric constant and distance of electrode during compression.•Microstructure and porous materials mainly enhance the capacitance change by reducing the Young's modulus.•The composite dielectric improve the sensitivity by increasing the relative dielectric constant.
Flexible pressure sensors have played a great role in acquiring information from human and automatics because of their wide use in electronic skin, soft robot, human-machine interaction and so on. Among a variety of flexible pressure sensors, capacitive pressure sensor has many advantages like simple structure, insensitive to temperature and humidity, low power consumption, etc. It is easy to fabricate such kind of pressure sensor, nevertheless, how to improve its sensitivity to broaden the high effective application has been a hotspot issue in recent years. In this paper, a large amount of research outputs on sensitivity improvement have been reviewed for flexible capacitive pressure sensor, including the aspects from introduction of performance evaluation indicators, working principle, generally used materials and capacitor structures to the methods of how to improve the sensitivity of capacitive pressure sensors. Then, the effective ways to obtain high sensitivity of pressure sensors have been compared and the development trend of flexible capacitive pressure sensor is prospected. This paper aims to provide references for the further research on the efficient fabrication of flexible capacitive pressure sensors and effective usage of such sensors in high sensitivity requirements of application areas.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
