Highly Stretchable Variable‐Transmittance Skin for Ultrasensitive and Wearable Strain Sensing

Recently developed strain sensors based on strain-induced change in resistance of semiconducting materials can be applied to human skin in future. However, the development of wearable strain sensors satisfying the requirements of large stretchability, broad sensing range, and electric stability remains a challenge. Here, strain-induced transmittance change in the TiO2 nanoparticles embedded in silicone film for realizing ultrasensitive strain detection is reported. The composite film with a 0.5% concentration of TiO2 nanoparticles exhibits a 76-fold larger transmittance variation ratio than that of the pure silicone film at 500% stretched strain. The flexible nanoparticle-elastomer composite material can be highly stretched by applying strain along any direction, leading to a wide and linear sensing range of up to 500% and a fast response time of smaller than 1.9 s. The device can be easily mounted on human skin for achieving wearable strain sensing to realize the motion detection of fingers.