Self-powered triboelectric sensor using GaN nanowires and stress concentration structure

Rapid advances in the internet of things have created various platforms for health monitoring, wearable devices, electronic skins, and smart robots. Practical realization of these new technologies inevitably requires a power supply. In this paper, we report self-powered triboelectric sensors (TESs), which incorporate GaN nanowires (NWs) grown on a Si(111) substrate as an active medium, and which are inspired by the structure of the human epidermis and dermis. The TESs were fabricated by stacking polydimethylsiloxane (PDMS) directly on GaN NWs on Si(111) and the formation of an electrode underneath the substrate. The PDMS layer forms interlocked nanoridge structures, which mimic the structure of the interface between the human epidermal and dermal layer, at the interface with the top surface of the GaN NWs. The interlocked nanoridge structures efficiently induce the transmission of stress to the underlying NWs, resulting in high triboelectric charge density and voltage. When the top surface of the TES was touched with a human finger, in the absence of an external power supply, maximum output voltage and power density of 14.7 V and 63.7 mW m^-2 were measured, respectively. These outputs are much higher than any of those that were previously reported.