Reduced Graphene Oxide Transparent Electrodes Enabling Compact Soft Tunable Lenses

Dielectric elastomer actuators (DEAs) are an electromechanically active polymer technology capable of producing large and fast controllable strains in thin, soft membranes. They are investigated to design electrically tunable optical devices for adaptive focusing, filtering, transmission, and camouflage. Some implementations of such devices can benefit from compliant electrodes that are also transparent. Here, we describe the development of such electrodes, by spray-coating a common DEA membrane with reduced graphene oxide (rGO). Increasing the rGO surface density from 0.10 to 0.17 µg/mm2, corresponding to an estimated thickness increase from ∼50 to ∼80 nm, reduced the sheet resistance from ∼600 to ∼15 kΩ/sq, while decreasing the optical transmittance at 550 nm from ∼42% to ∼17%. The application potential of the rGO electrode was demonstrated by its ability to enable a novel electrically tunable soft lens. The device consisted of a 12.5 mm-wide plano-convex PDMS lens coupled to a rGO-based transparent DEA, yielding a compact form factor. A driving electric field in the range 0–50 V/µm allowed for radially stretching the lens, to focus targets in the range 30–36 mm.