Self-rolling of vanadium dioxide nanomembranes for enhanced multi-level solar modulation

Thermochromic window develops as a competitive solution for carbon emissions due to comprehensive advantages of its passivity and effective utilization of energy. How to further enhance the solar modulation ( △ T sol ) of thermochromic windows while ensuring high luminous transmittance ( T lum ) becomes the latest challenge to touch the limit of energy efficiency. Here, we show a smart window combining mechanochromism with thermochromism by self-rolling of vanadium dioxide (VO 2 ) nanomembranes to enhance multi-level solar modulation. The mechanochromism is introduced by the temperature-controlled regulation of curvature of rolled-up smart window, which benefits from effective strain adjustment in VO 2 nanomembranes upon the phase transition. Under geometry design and optimization, the rolled-up smart window with high △ T sol and T lum is achieved for the modulation of indoor temperature self-adapted to seasons and climate. Furthermore, such rolled-up smart window enables high infrared reflectance after triggered phase transition and acts as a smart lens protective cover for strong radiation. This work supports the feasibility of self-rolling technology in smart windows and lens protection, which promises broad interest and practical applications of self-adapting devices and systems for smart building, intelligent sensors and actuators with the perspective of energy efficiency. In this work, authors demonstrate a smart window combining mechanochromism with thermochromism by self-rolling of VO 2 nanomembranes to modulate in-door temperature self-adapted to seasons and climate with high efficiency.