Miniature and tunable high voltage-driven soft electroactive biconvex lenses for optical visual identification

Abstract

Soft electroactive materials including dielectric elastomer (DE) and polyacrylamide (PAM) hydrogel have recently been investigated, which can provide exciting opportunities for optical imaging and biomedical engineering. We propose a tunable liquid lens based on PAM hydrogels, and the miniature lens is also composed of a dielectric elastomer actuator (DEA) and an ionic liquid enclosed. When a biconvex lens is fabricated, a bubble needs to be voided by controlling the pressure. The lens DEA based on PAM electrodes has various resistances that decrease with the stretch. However, it is a constant of 0.49 Ω for the DEA coupling carbon grease electrodes. In a high voltage-driven state, the curvature radius of the lens increased. As a result, the focal length was tuned and enlarged. Computational models are derived for the soft-actuated liquid lens, which improves the existing related theory by detail. Especially, the relationship between voltage and focal length is deduced and verified by experiments. The computational models and experimental phenomena are consistent. Moreover, an increase in pre-stretch and voltage produces a wider tenability range. This study opens the soft electroactive biconvex lenses in potential optical healthcare rehabilitation and optical visual identification applications.