Self-powered electrowetting optical switch driven by a triboelectric nanogenerator for wireless sensing

A self-powered electrowetting optical switch (EOS) was achieved by a combination of a freestanding sliding mode triboelectric nanogenerator (FS-TENG) and an electrically tunable liquid lens (ETULL). The ETULL was fabricated by a conducting fluid, an insulating oil, an acrylic cylindrical spacer as well as two indium tin oxide (ITO) electrodes. Upon applying a voltage on the ETULL, the interface between two liquids was curved due to the electrowetting effect, forming an insulating oil based concave lens. The light propagation through the ETULL could be switched between the on state, which means no light diverging at the flat interface, and the off state, where the light was diverged by the concave lens. The switch was controlled by the voltage generated by the FSTENG. To verify the effectiveness of the proposed self-powered EOS, a wireless sensing system was performed and the mechanical motions were remotely detected. Such a mechanical-electrical-optical signal conversion enables the wireless sensing, which can be applied for various fields such as human-machine interfaces, remote monitoring of the infrastructure health, security detections, wireless smart keyboard, etc.