Tunable window device based on micro-wrinkling of nanometric zinc-oxide thin film on elastomer

This Letter presents a tunable window device based on microscopic wrinkling of a transparent elastomeric surface. "Crack-free" microscopic wrinkling of a 50-nm ZnO thin film is possible on a highly adhesive acrylic elastomer membrane (VHB 4910) upon partial release from a large radial pre-stretch of membrane. This ZnO-based tunable window device demonstrates reversible tunability between transparent and translucent states. At zero compression with a flat surface, the device is transparent with a 93% in-line transmittance at 550-nm wavelength. At 14% radial compression with wrinkled surface, the device appears translucent with a 3% in-line transmittance. Analysis shows that a large amplitude and a small wavelength of transparent micro-wrinkles are good for refracting light diffusely. This method and material system are promising to make a low-cost, high-performance smart window.