Soft optical composites for tunable transmittance

We introduce a soft composite that is actuated mechanically to achieve switchable and tunable optical transmittance. Our design comprises a series of parallel opaque platelets embedded into an optically clear silicone-based elastomer matrix. Under an applied shear loading, the platelets rotate, thereby gradually increasing the transmittance of light through the device, in a controllable and reversible manner. Experiments on a prototype device are used to support finite element simulations that explore the parameter space of the system towards providing a set of design guidelines. Specifically, we study how the optical transmittance depends on the stiffness mismatch between the matrix and the platelets, as well as their initial orientation and aspect ratio. We also focus on the maximum attainable value of transmittance and the energetic requirements to achieve it. (C) 2016 Elsevier Ltd. All rights reserved.