Numerical modeling of tunable optofluidics lens based on combined effect of hydrodynamics and electroosmosis

Abstract

A numerical model of liquid-core liquid-cladding optofluidics lens under the combined effect of hydrodynamics and electroosmosis are presented in this paper. In the numerical simulation, a combined formulation using only one set of conservation equations to treat both fluids are employed. The coupled electric potential equation and Navier-Stokes equation are solved using the finite volume method. The level-set method is used to capture the interface between the fluids. To overcome a weakness in the level-set method, the localized mass correction scheme is applied to ensure mass conservation. The validity of the numerical scheme is evaluated by comparing with the experimental results; numerical results highlight the electroosmotic effect; the combined effect of pressure driven and electroosmosis can form optically smooth interfaces with arc-shape between the cladding fluids and the core fluid. Under fixed cladding flow rates, the same electric field forms symmetric biconvex lens only. Different electric fields can form biconvex lens, plane-convex lens, and meniscus lens. The results also present the velocity profiles and flow fields of micro lens. There is a good agreement between numerical and experimental results.