3D printed hydrogel for soft thermo-responsive smart window

Smart windows with tunable optical properties that respond to external environments are being developed to reduce energy consumption in buildings. In the present study, we introduce a new type of 3 D printed hydrogel with amazing flexibility and stretchability(as large as 1500%), as well as tunable optical performance controlled by surrounding temperatures. The hydrogel on a PDMS substrate shows transparent-opaque transition with high solar modulation(?Tsol) up to79.332% around its lower critical solution temperature(LCST) while maintaining a high luminous transmittance(Tlum) of 85.847% at 20°C. In addition, selective transparent-opaque transition above LCST can be achieved by patterned hydrogels which are precisely fabricated via a projection micro-stereolithography based 3 D printing technique. Our hydrogel promises great potential applications for the next generation of soft smart windows.