Soft tunable diffractive optics with multifunctional transparent electrodes enabling integrated actuation

We present a stretchable tunable transmissiongrating in which the optical surface serves simultaneously as anelectrode forelectrostatic actuation. Tunableoptics based onelastomers allow for a large tuning range, but integrating an actuator generally significantly increases the device footprint. By combining the optical and electrical functions into one multifunctional transparentmaterial, we use here thegrating as an integral part of adielectricelastomer actuator and hence avoid placing actuators around thegrating. The grating/electrode consists of a 750  nm thick soft ionogel, which is bonded on both sides of a 13 μm thick silicone membrane. The top ionogelelectrode is corrugated (2  μm pitch) and serves as thediffraction grating. The bottomelectrode is planar. Applying a voltage between theelectrodes generates a Maxwell pressure, leading to the in-plane expansion of theelastomer andelectrodes. The linear actuation strain of 12.8% is obtained at 1300  V. The ionogelgrating maintains accurately its period after 500 cycles and after one-month storage. The ionogelelectrodes present self-clearing properties, allowing the operation of the actuator close to the breakdown voltage. This device presents an unprecedented level of integration by making accurategrating structures directly on a transparent soft ionogel conductor, which opens broad possibilities for making tunableoptics.

Source: Applied Physics Letters - November 7, 2016 Category: Physics Authors: Xiaobin Ji, Samuel Rosset and Herbert R. Shea Source Type: research