Skin-integrated, stretchable, transparent triboelectric nanogenerators based on ion-conducting hydrogel for energy harvesting and tactile sensing

The high demand of flexible and biocompatible power supplies drives the research of soft and wearable triboelectric nanogenerators (TENGs), as which have been proven to be an outstanding candidate for energy harvesting. However, the reported wearable TENGs commonly face the hurdles of limited stretchability, poor transparency, low power outputs, and complicated fabrication processes. Herein, we report a single-electrode mode based transparent triboelectric nanogenerator (T-TENG), with remarkable electrical performance and good stretchability. A self-developed hydrogel (mainly composed of the interpenetrating polymer network and mobile ions) is applied as the conductive layer for the T-TENG, as which owns high stretchability (~850%), great electrical conductivity (1.2 S/m) and transparency of 90%. The great electrical performance of the TENG could be proven by the open-circuit voltage of ~684 V and short-circuit current of ~116 mu A under a gentle tapping force of ~16.67 kPa. The great outputs enable the T-TENG lighting up 360 light-emitting diodes (LEDs) at the same time. Moreover, the operational performance of the T-TENG is very robust where the outputs are almost unaffected after hundreds of cycles of stretching, folding, twisting, and smashing. To demonstrate its mechanical sensing capability, the T-TENG is attached to a finger to be bent, twisted, and folded, where there are clear electrical signals along with the deformations. With its high sensitivity, an 8 x 8 soft sensing array with low crosstalk is developed, and it could respond towards the gentle poking by finger in an accurate approach. The TTENG reported in this work demonstrates promising applications in the development of self-powered flexible electronics.