Highly Sensitive and Transparent Strain Sensor Based on Thin Elastomer Film

Abstract

Strain sensors of high sensitivity and excellent transparency were fabricated based on a thin ( $\sim 20~\mu \text{m}$ ) poly(dimethylsiloxane) (PDMS) elastomer film integrating a conductive composite of silver nanowires and neutral-pH poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate). Such a thin PDMS film was peeled off from a glass substrate, which surface was modified with a self-assembled monolayer to reduce the required tensile stress in the elastomer film for the peeling-off process. The thin film sensor presented a sensitivity more than 20 times higher than that of strain sensors based on a thick (800 $\mu \text{m}$ ) PDMS film, and also a high optical transparency of nearly 80%, which are the desired features for developing unperceivable and invisible sensors in wearable applications. Moreover, the sensor showed excellent durability and fast response/recovery speed. An application for real-time monitoring of human neck posture was finally demonstrated.