Ionic Liquid Enabled Transparent Heterogeneous Elastomers for Soft Electronics

Abstract Dielectric elastomer (DE), as an electrically active soft material, has enabled stretchable electronics, electronic skins, artificial muscles, biomimetic soft robots, and non‐magnetic motors. High permittivity is urgently desired for increasing the sensitivity of DE sensors and lowering the driving voltage of DE actuators. However, existing efforts for significantly enhanced permittivity is usually achieved at the expense of transparency of the DE by compositing external fillers, which limits the applications in optoelectronics, such as displays, touch screens, artificial eyes, etc. Here, by utilizing of transparent functional filler, ionic liquid micro‐droplet, and precise matching the refractive index with polydimethylsiloxane (PDMS) elastomer matrix, heterogeneous composites with high transparency and high permittivity are obtained simultaneously. The composites are transparent in the visible range (transmittance, 80%–95%). The permittivity reaches up to 22, which is more than seven times higher than the original value of the elastomer matrix. Moreover, the arbitrary deformability of ionic liquid filler endows the composites with better stretchability (300%) and much lower elastic modulus (0.5 MPa, about a quarter the value of PDMS), which is beneficial for soft electronics. Based on the as‐prepared high‐performance composites, high sensitivity and transparent soft sensors and touch panels have been realized, as well as wireless transmission of sensing signals.