Enhanced Sensitivity of Capacitive Pressure and Strain Sensor Based on CaCu₃Ti₄O₁₂ Wrapped Hybrid Sponge for Wearable Applications

Abstract

Pressure sensors with highly sensitive and flexible characteristics have extensive applications in wearable electronics, soft robotics, human–machine interface, and more. Herein, an effective strategy is explored to enhance the sensitivity of the capacitive pressure sensor by fabricating a dielectric hybrid sponge consisting of calcium copper titanate (CaCu3Ti4O12, CCTO), a giant dielectric permittivity material, in polyurethane (PU). An ultrasoft CCTO@PU hybrid sponge is fabricated via dip‐coating the PU sponge into surface‐modified CCTO nanoparticles using 3‐aminopropyl triethoxysilane. The overall results show that the –NH2 functionalized CCTO attributes proper adhesion of CCTO with the –OCN group of the PU to enhance interfacial polarization leading to a high dielectric permittivity (167.05) and low loss tangent (0.71) beneficial for flexible pressure sensing applications. Moreover, the as‐prepared CCTO@PU hybrid sponge at 30 wt% CCTO concentration exhibits excellent electromechanical properties with an ultralow compression modulus of 27.83 kPa and a high sensitivity of 0.73 kPa−1 in a low‐pressure regime (<1.6 kPa). Finally, pressure and strain sensing performance is demonstrated for the detection of human activities by mounting the sensor on various parts of the human body. The work reveals a new opportunity for the facile fabrication of high performance CCTO‐based capacitive sensors with multifunctional properties.

Micro‐Nano Processing of Active Layers in Flexible Tactile Sensors via Template Methods: A Review

“…Over the past decade, a series of conductive materials, such as Ag NWs, [71] graphene, [72] CNTs, [73] and ITO [74] have been explored as electrode materials for capacitive tactile sensors. All sorts of low elastic modulus materials including PDMS, [75] Ecoflex, [76] and PU [77] have also been investigated as sensing layers. Recently, the introduction of micro-nano structures such as micropyramid, [78] micropillar, [79] and microdome [80] have enabled the Pressure sensitivity: from 0.03 to 0.55 V kPa −1 Bending sensitivity: from 0.01 to 0.1 V per degree [35] Cone-like array microstructures Sensitivity: from 9.08 to 127.22 mV kPa −1 [41] sensing layer to possess better mechanical properties, greater compressibility, and higher sensitivity under tiny pressure.…”

Ionogel-based flexible stress and strain sensors

“…Conversely, strain sensors are more responsive to their deformation, and are flexible devices with excellent deformation ability and elastic recovery ability [9][10][11][12]. Some flexible sensors sensitive to both stress and strain can detect pressure and strain, respectively [13][14][15][16].…”

Adjusting Sensitivity and Linearity of the Wearable Pressure Sensors by an Arbitrary Micro‐Protuberance Structure of Polyvinylidene Fluoride/Reduced Graphene Oxide Dielectric Films

“…In the past decade, capacitive pressure sensors have attracted significant research concentrations because of their simple structure, high‐drift stability, and low power consumption characteristics. [ 1,2 ] Moreover, recent significant progress in sensor structures, [ 3,4 ] dielectric materials, [ 5,6 ] and manufacturing processes [ 7,8 ] made various new applications achievable, such as in artificial skin, [ 9 ] wearable medical devices, [ 10 ] user‐interactive interfaces, [ 11 ] etc. Typically, Bao and co‐workers [ 12 ] fabricated a soft electronic skin based on pyramids and hills patterned electrodes of carbon nanotube polyurethane (PU), which can discriminate, in real time, both normal and shear forces.…”