A Computational Model Of Tunable Lenses With Soft Dielectric Materials

Lenses using transparent dielectric elastomers membranes and liquid are constructed by two different methods.One type is called separation tunable lens and another one is called integrated tunable lens,which change its focal length by altering the voltage applied on themselves.To make lenses be better applied,designer should figure out the relationship between voltage and focal length and impact imposed by the characteristics of lens,such as the pre-stretch of dielectric elastomers,the proportional size and the volume of liquid.Furthermore,the modes of failure should be predicted to make sure that the lenses work safely and efficiently.In this paper,to meet above demand,work has been done as follows:1.First,we analyse the deformation of dielectric elastomers and find that although there is inhomogeneous on the boundary,its scale is so negligible and has little impact on focal length.Thus,we adopt homogeneous deformation assumption.2.According to the homogeneous deformation assumption and energy method,governing equations of the lenses are established.3.The material model of dielectric elastomers is to be prescribed and the stress and the stretch in the elastomer membranes should be derived from the above material model.Governing equations of the lenses are simplified to be solved.4.We compare the computational results and the experimental results and find the solutions of stress,stretch and electric strength.We also make clear that how the relationship between the voltage and the focal length is influenced by the characteristics of lenses.Results show that:1.The computational results of homogeneous deformation agreeing well with the experimental results can predict the relationship of the voltage and focal length accurately.2.During the actuation,the lenses would not fail.3.The pre-stretch of dielectric elastomer membranes and proportional size of lenses have a large effect on the relationship of the voltage and the focal length whereas the volume of liquid does not.For the computational model of two kinds tunable lens,the governing equation is fairly simple,and the process of computational is concise.Therefore,it is very convenient for designers to refer.