Smart Curtains for Spontaneous Solar Modulation via Natural Light-Triggered Deformable Shading and Chromogenic...

Smart windows, fabricated from stimulus-responsive chromogenic materials, can modulate the transparency of a window toward sunlight to control room temperature. The widespread implementation of this technology can improve indoor comfort and effectively reduce energy consumption. However, due to their initial optical properties, chromogenic materials in solid-state smart windows continue to absorb sunlight, causing overcooling and temperature instability. Here, stimulus-responsive chromogenic nanowires (NWs) and photothermal actuators are combined to create flexible, macro-deformed smart curtains. The difference in thermal expansion coefficient between bacterial cellulose and polyethylene in actuators allows the smart curtains to keep curled at low light intensities (off-state) and unroll under intense light (on-state). The solar modulation efficiency is further enhanced by the synergy of chromogenic (thermochromic or photochromic) NWs. When rolled up, the smart curtains allow ample sunlight to pass through ordinary windows (92.0% of solar radiation) for heating. They can achieve temperature reductions exceeding 6.0 °C, attributed to the regulation of solar radiation, with 62.3% for thermochromic smart curtains and 79.1% for photochromic smart curtains. Besides, the smart curtains can be mounted directly on the building frame without replacing existing windows. These results illustrate the feasibility of smart curtains and represent a conspicuous step toward sustainable building technologies.