Modelling of a soft tunable lens actuated by an annular dielectric elastomer actuator with homogeneous and inhomogeneous prestretches

Abstract

Abstract Unlike the conventional tunable lens which contains cumbersome elements to fulfill the focus adjustment, soft liquid lens shows distinct advantages in compactness and flexibility. This paper presents a computational model of a dielectric elastomer (DE)-based, liquid-coupled soft tunable lens. The vital component of the lens system is a DE film which is divided into lens part and actuation part. The actuation part is annular which is coated with compliant electrodes while the lens part is circular and uncoated. A fixed volume of glycerol is injected into the lens to act as a transparent medium. An applied voltage will trigger the transmission of liquid between the two parts and eventually change the focal length. Governing equations for the two parts are established and the shooting method with two initial guesses is developed to solve the boundary value problems. The simulation results agree well with the experimental data. Several parametric analyses are carried out based on the developed model. It is found that the film thickness, initial volume of the liquid, the prestretch, and areas of the two parts all have significant effects on the focusing ability of the tunable lens. Both the homogeneous and inhomogeneous prestretched schemes are considered. An inhomogeneous prestretch on the annular actuation part is beneficial for improving the focusing ability of the tunable lens.