A liquid lens based on electrowetting

Abstract

A primary goal of this work is to develop and characterize a novel liquid lens based on electrowetting. A droplet of silicone oil confined in an aqueous solution works as a lens. Electrowetting then controls the shape of the confined silicone oil, and the focal length may be varied upon an applied electric potential. The planar lens design is employed for easy integration of a lens system into a microfluidic device. The achievements of this work are to develop an electrowetting-based planar liquid lens without an off-the-plane electrode structure and to demonstrate the planar liquid lens with variable focal length control. Electrowetting has recently become popular in many applications including a liquid lens. However, reported liquid lenses based on electrowetting had a limitation of integration onto a lab-on-a-chip system due to their off-the-plane electrode structures. In order to overcome the structural issue, a planar liquid lens is proposed in this thesis. A silicone oil droplet confined in an aqueous solution acts as a lens material. Planar ring-type electrodes control the confinement of silicone oil by electrowetting. With an applied potential, the surface above the ring-type electrodes becomes hydrophilic and attracts the surrounding aqueous solution making the confined silicone oil more curved. By charging the curvature of the lens, the focal length can be controllable. As the lens is in a planar shape, it will be simple to integrate the planar lens on a microfluidic system. The lack of a vertical wall requirement in the demonstrated liquid lens eliminates the limitation of the integration issue for lab-on-a-chip systems. In addition, due to the controllable variable focal length of this lens, it is applicable to various optical applications which need an integrated and controllable lens.