A fully self-powered cholesteric smart window actuated by droplet-based electricity generator*

Self-powered smart windows are highly attractive for the development of energy-efficient buildings system, owing to its superior capacities in regulating the energy and information exchange between indoor and outdoor environments. Although immense achievement has been made in the self-powered cholesteric liquid crystal smart window (CLC-SW) based on triboelectric nanogenerators (TENGs), such a self-powered manner is limited by some challenges such as the need of the continuous input of external forces, as well as unstable performance owing to inevitable mechanical abrasion of TENGs surface. Here, we develop a fully self-powered cholesteric LC-SW by leveraging droplet-based electricity generator (DEG) as spontaneous and sustained energy reservoir, in which DEG has superior capacities to harvest ceaseless energy from ambient environment and circumvent any additional electrical power input. We demonstrate that DEG-driven CLC-SW exhibits a rapid response and high tunability in the transformation between the transparent state and the hazy state in a wide range of solar spectrum. Distinct from the conventional smart windows, both transparent and hazy modes of DEG-driven CLC-SW can be self-sustained for a long time, and also be reversibly switched by the gentle mechanical pressure-loading. The DEG-driven smart window developed in our work can also find some applications such as indoor temperature modulation and privacy information protection.