Highly Stretchable and Transparent Conductive Electrodes for Resistive Strain Sensors

Conductive organic materials are a crucial component of resistive strain sensors because phase separation limits the concentration of inorganic materials in polymer matrices, leading to poor electrical conductivity. However, traditional conductive polymers are not good candidates for use in flexible electric devices due to their low or ultralow sensitivity and stretchability. In this paper, the development of transparent, highly stretchable polymer electrodes by a one-step solution process is reported. The polymer electrodes tolerate extreme strains exceeding 150% and feature an ionic conductivity of 1.4 x 10(-4) S cm(-1). These metal-free electrodes also exhibit a high optical transparency of 60%, suggesting that they have great potential for optoelectronic applications. Strain sensors are fabricated by covering the conductive polymer electrodes with polyimide film in a simple, low-cost, and scalable process. The as-assembled strain sensors can be used for both stretching and compressing with high sensitivity (a maximum gauge factor of 1049.9), an ultralow limit of detection (0.5% strain), and excellent reliability and stability (>5000 stretching cycles).