Flexible strain sensors have enormous potential in wearable devices, robots, and health monitoring equipment. However, the poor stretchability of strain sensors based on semiconductors and the low sensitivity of resistance change‐based hydrogel strain sensors hinders the comprehensive application. Herein, a flexible piezoionic SnSe‐hydrogel composite with an optimized structure and improved performance is designed. The piezoionic output rises nonlinearly as the applied force increases, with the piezoionic coefficient up to 1780 nV Pa−1 and −7.21 nA Pa−1. The composite can realize the continuous positioning in 1D space based on the piezoionic effect. It also demonstrates self‐powered characteristics, an ultrafast response speed of 6–8 ms, and a high gauge factor of 95.89. The sensor is exemplified to monitor fist clenching and finger bending, which has the potential to discriminate different joint movements. Meanwhile, the device can light up a light–emitting diode under pressure and bending. The as‐prepared piezoionic SnSe‐hydrogel device, having both high stretchability and sensitivity, may shed light on developing high‐performance flexible strain sensors and generators.

The remarkable properties of layered semiconductor nanosheets (LSNs), such as scalable production, bandgap tunability and mechanical flexibility have promoted them as promising building blocks for nanoelectronics and bioelectronics. However, it...

Soft optoelectronics that can be naturally conformable to human skins for noninvasive light-tissue interplays are inspiring for the realization of human–machine interactions, health monitoring, and soft robotics. Advances in material and structural engineering have been made to realize various skin-like electronics/optoelectronics. However, there still exist great challenges such as procedure complexity and high-power dissipation that seriously impede practical applications for these devices. In this work, we demonstrate a fully stretchable and skin-mountable ionic-gated organic phototransistor with an ultra-low power dissipation of 3 nW, high sensitivity up to 103, and a mechanical stretchability of ε = 20%. The phototransistor is composed of an elastomeric ionic gate dielectric layer with ultrahigh capacitance over 1 μF/cm2 and high stretchability up to ε = 50%. Strain-insensitive photodetection of the device is achieved by the nanoconfinement effect existing inside the intrinsically stretchable photoactive semiconductor layer via blending elastic and insulative polymers into an organic bulk heterojunction. Combining with its pronounced electromechanical properties, the stretchable photodetector can be conformable to various body parts for real-time and noninvasive monitoring on different pulse-waves, demonstrating the ability of low-cost and in-home supervision on chronic diseases in daily life.