Enhancing Accuracy of Flexible Piezoresistive Pressure Sensors by Suppressing Seebeck Effect

Flexible piezoresistive pressure sensors can offer convenient detection of mechanical deformations for wearable electronics.Previous studies of flexible piezoresistive pressure sensors focus on the sensitivity but the low-cost and self-powered sensors remain a challenge due to the deviation of resistance signal acquisition caused by thermoelectric voltage.Here,piezoresistive pressure sensors with ultralow Seebeck coefficient of-0.72μV/K based on carbon nanotubes(CNTs)/polyethyleneimine(PEI)/melamine(CPM)sponge are reported.Due to the diminished Seebeck effect,the CPM sponge pressure sensors successfully reduce the deviation to 18.75%and can keep stable sensitivity and resistance change under a very low working voltage and change temperature environment.The stable properties of the sensors make them successful to work for real-time sensing in self-powered wearable electronics.

Bioinspired flexible piezoresistive sensor for high-sensitivity detection of broad pressure range

The human skin has the ability to sense tactile touch and a great range of pressures.Therefore,in prosthetic or robotic systems,it is necessary to prepare pressure sensors with high sensitivity in a wide measurement range to provide human-like tactile sensation.Herein,we developed a flexible piezoresistive pressure sensor that is highly sensitive in a broad pressure range by using lotus leaf micropatterned polydimethylsiloxane and multilayer superposition.By superposing four layers of micropatterned constructive substrates,the multilayer piezoresistive pressure sensor achieves a broad pressure range of 312 kPa,a high sensitivity of 2.525 kPa^(−1),a low limit of detection(LOD)of<12 Pa,and a fast response time of 45 ms.Compared with the traditional flexible pressure sensor,the pressure range of this sensor can be increased by at least an order of magnitude.The flexible piezoresistive pressure sensor also shows high robustness:after testing for at least 1000 cycles,it shows no sign of fatigue.More importantly,these sensors can be potentially applied in various human motion detection scenarios,including tiny pulse monitoring,throat vibration detection,and large under-feet pressure sensing.The proposed fabrication strategy may guide the design of other kinds of multifunctional sensors to improve the detection performance.

Highly sensitive piezoresistive pressure sensors based on laser-induced graphene with molybdenum disulfide nanoparticles

Wearable pressure sensors have drawn significant attention because of their extensive applications in motion detection, tactile sensing, and health monitoring. However, the complex manufacturing process and high cost of active materials make low-cost,large-scale production elusive. In this work, we report a flexible piezoresistive pressure sensor assembled with two 3D laserinduced graphene(LIG) foam electrodes on a polyimide thin film from a simple laser scribing process in the ambient environment. The design of the air gap between the two foam electrodes allows the sensor to showcase a low limit of detection of 0.274 Pa, which provides favorable sensing performance in motion detection and wrist pulse monitoring. The addition of spherical MoS2 nanoparticles between the two foam electrodes further enhances the sensitivity to 88 k Pa-1 and increases the sensing range to significantly outperform the previous literature reports. The demonstrated LIG pressure sensors also exhibit fast response/recovery rates and excellent durability/repeatability.

High-performance Multilayer Flexible Piezoresistive Pressure Sensor with Bionic Hierarchical and Anisotropic Structure

Flexible pressure sensor that enables detection of multimodal signals has greater advantages in human–computer interaction,medical/health care,and other applications.To make a versatile flexible pressure sensor,hierarchical and anisotropy structure are key features to improve sensing performance and realize multi-signal detection.However,traditional flexible sensors usually have narrow linear range and single signal detection capability.Herein,a highly sensitive flexible piezoresistive pressure sensor which has broad linear range of pressure is developed by replicating one dimensional microstructures from reed leaf and using multilayer superposition of micropatterned polydimethylsiloxane(m-PDMS).Through superposing 4 layers of parallel micropatterned constructive substrates,the multilayer piezoresistive pressure sensor exhibits a high sensitivity of 2.54 kPa?1,a fast response time of 30 ms,and a broad linear range of 107 kPa.The flexible piezoresistive pressure sensor is also highly robust:there is no fatigue after testing for at least 1000 cycles.Due to the specific anisotropy of the micro-structure,the sensor can measure the tangential force in different directions.It permits multimode signal detection,including pressure,tangential force,and deformation.The versatile flexible pressure sensor enables effective monitoring of multisignals,it reveals great potential for medical and health care,flexible human–computer interaction,and intelligent robot.

Pressure and Arc Voltage Measurement in a 252 kV SF_6 Puffer Circuit Breaker

The pressure distribution in an arcing chamber is critically important for the SF6 puffer circuit breaker design. In this paper, the pressure variation of four locations in the nozzle was measured by piezoresistive and fiber optical pressure sensors at two current levels of 10 kA and 50 kA. An arc voltage measurement was also taken. The results demonstrate that using either type of sensor with a connecting tube is able to detect the fast pressure variation in circuit breakers, however the possible distortion and delay to the pressure transient caused by the tube need further study.

Polymer-derived SiBCN ceramic pressure sensor with excellent sensing performance

Pressure measurement with excellent stability and long time durability is highly desired,especially at high temperature and harsh environments.A polymer-derived silicoboron carbonitride(SiBCN)ceramic pressure sensor with excellent stability,accuracy,and repeatability is designed based on the giant piezoresistivity of SiBCN ceramics.The SiBCN ceramic sensor was packaged in a stainless steel case and tested using half Wheatstone bridge with the uniaxial pressure up to 10 MPa.The SiBCN ceramic showed a remarkable piezoresistive effect with the gauge factor(K)as high as 5500.The output voltage of packed SiBCN ceramic sensor changes monotonically and smoothly versus external pressure.The as received SiBCN pressure sensor possesses features of short response time,excellent repeatability,stability,sensitivity,and accuracy.Taking the excellent high temperature thermo-mechanical properties of polymer-derived SiBCN ceramics(e.g.,high temperature stability,oxidation/corrosion resistance)into account,SiBCN ceramic sensor has significant potential for pressure measurement at high temperature and harsh environments.

Highly pressure-sensitive graphene sponge fabricated by γ-ray irradiation reduction

Graphene sponge(GS) with microscale size, high mechanical elasticity and electrical conductivity has attracted great interest as a sensing material for piezoresistive pressure sensor. However, GS offering a lower limit of pressure detection with high gauge factor, which is closely dependent on the mechanical and electrical properties and determined by the fabrication process, is still demanded. Here, γ-ray irradiation reduced GS is reported to possess a gauge factor of 1.03 kPa^–1 with pressure detection limit of 10 Pa and high stress retention of 76% after 800 cycles of compressing/relaxation at strain of 50%. Compared with the carbon nanotube(CNT) reinforced GS, the improved lower limit of pressure detection and gauge factor of the GS prepared by γ-ray irradiation is due to the low compression stress(0.9 kPa at stain of 50%). These excellent physical properties of the GS are ascribed to the mild,residual free, and controllable reduction process offered by γ-ray irradiation.

具有超高灵敏度、宽工作范围、低检测限的3D气凝胶可穿戴压力传感器用于语音识别和生理信号监测

随着智能电子设备的快速发展,对同时具有超高灵敏度、宽工作范围、低检测限的可穿戴压力传感器的需求越来越大.本文开发了一种基于超轻(29.5 mg cm^(-3))和弹性的3D壳聚糖/MXene(CS/MXene)复合气凝胶的压阻式压力传感器.由于CS和MXene之间的强静电吸引力,具有良好机械性能的CS/MXene气凝胶只需一步冷冻干燥即可获得,无需额外的化学处理.CS/MXene复合气凝胶压力传感器在小压力区(<1 kPa)和大压力区(1-20 kPa)的灵敏度分别为709.38和252.37 kPa^(-1).在此压力范围下,其灵敏度是目前报道的同类型气凝胶压力传感器的最高值.此外,该传感器具有快速的响应时间(<120 ms)、1.4 Pa的超低检测限以及10,000次循环后几乎无衰减的良好稳定性.以上出色的性能不仅使得该传感器可用于检测肢体活动和空间压力分布等较大幅度的压力信号,而且还能准确检测脉搏、语音等微小压力信号.这种多功能的柔性压力传感器极大地拓宽了可穿戴电子器件在语音识别、健康监测和人机交互等诸多领域的应用范围.

A novel algorithmic method for piezoresistance calculation

A novel algorithmic method, based on the different stress distribution on the surface of thin film in an SOI microstructure, is put forward to calculate the value of the silicon piezoresistance on the sensitive film. In the proposed method, we take the Ritz method as an initial theoretical model to calculate the rate of piezoresistance ΔR/R through an integral （the closed area Ω where the surface piezoresistance of the film lies as the integral area and the product of stress σ and piezoresistive coefficient π as the integral object） and compare the theoretical values with the experimental results. Compared with the traditional method, this novel calculation method is more accurate when applied to calculating the value of the silicon piezoresistance on the sensitive film of an SOI pieoresistive pressure sensor.