Actuating Fluid–Fluid Interfaces for the Reconfiguration of Light

Advances in microfluidics and the associated ability to manipulate fluidic interfaces in the submillimeter scale have fueled the rapid development of a new class of highly reconfigurable optofluidic devices. In this type of devices, the optical interface is formed at the interface between two fluids. Actuation of the shape or the position of the fluidic interface allows dynamic reconfiguration of the optical properties of the device. Since a fluidic interface is intrinsically smooth as a result of minimization of interfacial energy, polishing is unnecessary in these optofluidic devices. It is also simple to obtain a graded profile of refractive index by using diffusion between miscible liquids possessing different refractive indices. This paper aims to review recent development of optofluidic devices based on the actuation of fluid-fluid interfaces, and also to illustrate their principles of operation.