Durable and Scalable Mechanochromic Smart Windows for On-Demand Privacy and Energy Saving

Smart windows can offer on-demand privacy and enhance building energy efficiency by dynamically regulating optical transmittance, but most current systems have limited modulation ability and poor long-term durability. Mechanochromic smart windows offer promising advantages, including simple construction, rapid response, and zero power consumption in static mode. Here, we present a scalable all-silicone mechanochromic elastomer (ASMCE) for a smart window that achieves broadband optical modulation across the visible and near-infrared spectrum via a micrometer-pore scattering strategy. Beyond effective visible light modulation, this design delivers an ultrahigh solar modulation ability (ΔTsol) of 75.8% over 0-80% strain, one of the highest values reported for smart windows. The ASMCE comprises a polydimethylsiloxane (PDMS) matrix embedded with polymethylsilsesquioxane (PMSQ) microspheres with compatibility for meter-scale roll-to-roll fabrication at low cost, ensuring scalability for real-world applications. Excellent durability is demonstrated under accelerated aging (190 days at 80 °C/90% RH), outdoor exposure (1 year), and cyclic stretching (1000 cycles). Thermal tests and building-scale simulations confirm superior on-demand indoor light/temperature regulation and energy savings. This work introduces a durable, scalable smart window platform for high-performance optical modulation and sustainable building energy management.