Smart glass or switchable transparency panels are being commercialized for applications ranging from privacy panels to controlling solar load for buildings and vehicles. However, the technologies that have been developed such as electrochromic, polymer dispersed liquid crystal, and suspended particle devices are complex and expensive, and additionally switch from partial transparency to a tinted or scattering state, not having a highly reflective state, which limits applications. Our group has developed an optofluidic smart glass which should have 10x lower cost than current technologies. It is based upon a reflective structure that switches to transmissive by introducing an index-matching fluid. Previously, we have shown such a panel that consists of a solid plastic corner-cube array with a thin cavity behind it. With air in the cavity the panel is highly reflective based upon total internal reflection. We have shown inexpensive index matching fluids that when pumped into the cavity result in near-perfect transparency. However, our corner-cube array panels suffer from transmission at angles larger than 20 degrees in the reflective state. This transmission is refractive passing oblique rays at a different angle than line-of-sight, but nonetheless compromises performance. Here, we show a two-layer structure consisting of two one-dimensional solid corner reflector arrays with the layers having rotated axes. Rays beyond the TIR angle for one layer are refracted below the TIR angle for the second layer. Each layer has a cavity layer for introducing index matching fluid, and we show high transmission switching up to 60 degrees.
Dan Wolfe and K. W. Goossen, "Optofluidic smart glass with wide angular performance," Proc. SPIE 10601, Smart Materials and Nondestructive Evaluation for Energy Systems IV, 1060102 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 05, 2018; Published: 27 March 2018); https://doi.org/10.1117/12.2296410.
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