Variable-Focus Liquid Lens Based on EWOD

A novel configuration of variable-focus liquid lens based on electrowetting-on-dielectric (EWOD) technique is presented, which consists of a glass slide coated with a conductive indium-tin-oxide (ITO) film and a hydrophobic dielectric film, a hollow conical metal ring suspended right above the gap between the slide and the ring, and the lens liquid (water). By varying the voltage applied to grounded metal ring and the ITO control electrode, both the position and curvature of the liquid meniscus can be reversibly adjusted, thus, tuning the focal length of the lens. The experimental results show that at a 40 V power supply, the liquid lens is able to focus on objects away from 2.5 cm up to infinity with a good imaging quality. (C) Koninklijke Brill NV, Leiden, 2011