Flexible pressure sensors based on three-dimensional porous elastomeric structures

Abstract

In this dissertation, we propose novel flexible pressure sensors based on the mechanical, electrical, and optical characteristics of microporous elastomeric structures. First, we report a flexible and wearable piezocapacitive pressure sensor based on a three-dimensional (3-D) microporous dielectric elastomer, which is capable of highly sensitive and stable pressure sensing over the entire tactile pressure range (~130 kPa) via a facile and cost-effective process. The microporous dielectric elastomer can provide perfectly reversible and elastic compressive behavior while micropores are closed and opened without viscoelastic behavior, which is generally considered as the major cause of hysteresis. Based on the compressive behavior of the microporous structure under external pressure, we successfully achieved outstanding sensor performance with high sensitivity of 0.601/kPa^{-1} at 5 kPa and a wide dynamic range of 0.1 Pa - 130 kPa without a significant reduction in the sensitivity. We have demonstrated that our sensor can be easily utilized as a wearable pressure-sensing device in the form of a pressure-sensing skin for seizing force measurements of robotic fingers and as a bandage-type wrist-pulse-monitoring device. Finally, a sensor array pad was fabricated for the detection of spatially distributed pressures. Second, we report a novel self-powered flexible optical pressure sensor based on a porous elastomer film as a light transmission medium with ultra-high sensitivity and wide dynamic range covering the tactile pressure range. The pore-closing behavior under external pressure and the corresponding change of light transmittance of the microporous elastomer film were investigated. The microporous elastomer film based optical pressure sensor showed highly sensitive and stable performance with the sensitivity of 0.101/kPa^{-1} over the pressure range of 0-150 kPa. Finally, the self-power-generating wearable human motion sensor platform was demonstrated for the detection of flexion/extension motion of a human finger.