A fully self-powered, ultra-stable cholesteric smart window triggered by instantaneous mechanical stimuli

Abstract

ABSTRACT Smart windows (SWs), especially self-powered SWs, are desirable in a great variety of applications. Nowadays, nearly all SWs require continuous power supply enabled by batteries or energy harvesters such as solar cells, etc. However, batteries are usually with limited lifetime and potential environmental issues, while solar cells largely depend on the weather conditions. In this work, a fully self-powered, instantaneous-mechanical-stimuli-triggered, normally transparent smart window was developed based on an elaborately tailored cholesteric liquid crystal (LC) and a freestanding sliding triboelectric nanogenerator (FS-TENG). The transparency switching including transparency-to-haziness and haziness-to-transparency are facilely triggered by instantaneous TENG-charging and pressure-loading, respectively, with the high transparency contrast of 71.5% and the haze contrast of 61.8%. Both transparent and opaque modes can sustain for an extremely long time without continuous power supplies from energy harvesters. The smart window demonstrated in this work shows the capability of fully self-powered irradiation control for indoor temperature modulation and battery-free privacy information protection while the continuous power supply is no longer required, benefiting a wide variety of fields such as self-powered sunroofs, smart farming systems, motion-driven privacy protection systems, etc.