Self-Powered Optical Switch Based on Triboelectrification-Triggered Liquid Crystal Alignment for Wireless Sensing

Here, a self-powered optical switch (OS) composed of a surface-etched single-electrode triboelectric nanogenerator (TENG) and a polymer-dispersed liquid crystal (PDLC) film is reported. The working principle of the developed OS is that the liquid crystal alignment can be driven by triboelectrification-generated voltage, inducing the PDLC film to rapidly switch its initial translucent state to an instantaneous transparent state. An output voltage of 360 V is generated upon the PDLC film when a nitrile rubber film contacts with the TENG at an area of 25 cm ² and a velocity of 0.4 m s ⁻¹ . As such, a wide dimming range with the relative transmitted light intensity from 0.05 to 0.85 can be achieved for the OS. Enabled by the unique mechano-electro-optical reaction, the effects of a series of structural parameters on the performance of the OS are methodically studied. Particularly, through integrating the OS with a visible-light-operated signal-processing circuit, a complete wireless sensing system with a fully power-free sensing node is developed. The paradigms of hand touching and foot stepping triggered wireless alarms are demonstrated, explicitly showing great potential for the system in many possible interactive human–machine interface applications, such as surveillance, security systems, remote operation, and automatic control.