Tunable liquid micro-lens system

Electro-wetting technology has become a promising approach for the fabrication of liquid micro-lenses with tunable focal length. By applying a voltage between a liquid droplet and an electrode covered by an insulating layer, the surface free energy, and thereby the contact angle of the droplet, is modified. By embedding the droplet in a fluid of the same density, the influence of gravity can be removed and a maximum of mechanical stability can be reached. A novel, tunable liquid micro-lens system fabricated in MEMS technology is presented and characterization results using three kinds of liquids, including an equal-density fluid system, are presented. The back focal length of this latter system can be tuned between 2.3 mm and infinity with applied voltages of 0 V to 45 V.