3D model for rectangular electrowetting lens structures

The electrowetting-on-dielectric (EWOD) lens is a good candidate for dynamic beam-shaping optics for advanced solid-state lighting systems. A geometric approximation model is described to predict the meniscus shape of a rectangular EWOD lens with arbitrary voltages and small Bond numbers. The model approximates the meniscus geometry as being a part of a compound toroidal surface. The model was compared with free-energy minimization simulations and experiments with the largest standard deviation between the geometric model and the simulation for a wide variety of bias voltages being less than 2%. The experimental validation compared the measured dynamic image shifts of a wire mesh produced with test EWOD cells with the predicted image obtained from the toroidal geometric model using a ray-tracing simulation. The optical performance of the experimental 3D electrowetting lens is described and was found to agree reasonably well with the predicted optical performance of the geometric model for a wide variety of operating conditions.