Environmentally responsive active optics based on hydrogel-actuated deformable mirror arrays

We report hybrid polymer actuator arrays based on environmentally responsive hydrogel and actuatable optical microstructures that are designed to reversibly switch optical properties in response to the environment. Arrays of micrometer scale plates were patterned by deep reactive ion etching of silicon which served as master structures for replica molding in polydimethylsiloxane (PDMS). UV-curable epoxy was cast in a metal-sputtered PDMS mold to transfer a thin metal film onto each microplate to form a micromirror array. Polyelectrolyte hydrogel, such as poly(acrylamide-co-acrylic acid), was patterned on the micromirror array and acted as an artificial muscle, bending the micromirrors in response to the change in humidity or pH. Such hybrid systems showed reversible switching between high transmittance (low reflectivity) and low transmittance (high reflectivity) without the aid of external power. Our design of hybrid actuated optics opens a broad avenue for developing environmentally responsive adaptive and active optics.