Porous Microstructure‐Assisted Flexible and Highly Sensitive Polymer Piezoresistive Pressure Sensor

Abstract

Flexible and wearable pressure sensors are gaining attention due to their widespread applications in biomedical, intelligent, and smart systems. However, developing highly sensitive sensors for low pressures and wide ranges is still a challenge. In this direction, a flexible PDMS‐based pressure sensor is presented, having hemispherical microstructures to achieve high sensitivity and operation range. Several experiments with various dimensions have demonstrated that the sensor with microstructures of radii 100 μm on a 0.5 mm‐thick substrate shows optimum performance for a low‐pressure range of less than 6 kPa. Further, a finite‐element method‐based simulation has illustrated improvement in the sensor response with the decrease in substrate thickness. In practice, a very thin film of the substrate is not suitable for detecting a wide range of pressure. The presence of microstructures, however, improves the performance. Adding porosity to the substrate further elevates the sensitivity to 9.51 kPa−1 for a low‐pressure range of less than 10 kPa. Even for medium (30–70 kPa) and high‐pressure ranges (40–120 kPa), the sensitivities of the sensor proposed are as high as 0.045 and 0.17 kPa−1, respectively. The proposed sensors show at least an order improvement of sensitivities compared with the prior arts.

Plastic Deformation in a Molecular Crystal Enables a Piezoresistive Response

“…[ 28 ] There are many kinds of sensors available including capacitive sensors, [ 29–31 ] electrochemical sensors, [ 32 ] piezoelectric sensors, [ 33 ] piezoresistive sensors, etc. [ 34–38 ] A reversible change in the resistivity of the material with pressure can make it employable in stress or strain‐based sensors. [ 39 ]…”

“…[28] There are many kinds of sensors available including capacitive sensors, [29][30][31] electrochemical sensors, [32] piezoelectric sensors, [33] piezoresistive sensors, etc. [34][35][36][37][38] A reversible change in the resistivity of the material with pressure can make it employable in stress or strain-based sensors. [39] Here we show that single crystals of 4-trifluoromethyl phenyl isothiocyanate (4CFNCS, 1) can be readily bent, twisted and coiled, and a combination of nanoindentation, DFT calculations and micro-focus synchrotron X-ray diffraction studies have been employed to explore the mechanism of these mechanical responses.…”

Recent progress in flexible pressure sensors based on multiple microstructures: from design to application

“…Depending on the sensing mechanism, several types of FPSs have been explored, including piezoresistive, 28,38,39 capacitive, [40][41][42][43] piezoelectric, [44][45][46][47] triboelectric, 48-51 ionic, 22,23,52 and hybrid response pressure sensors. 24,25 The diversity of active materials and structural designs allows sensors designed based on different sensing mechanisms to have unique sensing characteristics.…”

“…38 The design of piezoresistive FPSs can be divided into four types: fabrication of a micro-patterned structure flexible layer, 53 an elastic porous conductive layer, 54,55 a fiber network layer 56 and other designs. 39 For a given material, micropatterns and porous structures are often applied because this low-modulus design facilitates sensitivity and adjustment over a large pressure range. In addition, a field effect transistor-based pressure sensor can be prepared by combining a flexible pressure sensor with a field effect transistor (FET) and connecting a varistor to the source/leakage electrode of the FET.…”

Self‐Powered Rapid Response Flexible Pressure Sensor for Wearable Application

“…[5][6][7] Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, energy harvesters, and more. According to the pressure-sensing principle, flexible pressure sensors can be divided into capacitive, [8][9][10] resistive, [11][12][13] and piezoelectric. [14][15][16] Compared with the first two, piezoelectric pressure sensors can passively generate piezoelectric potential without external excitation power and thus can be easily fabricated into wearable devices.…”