Tunable-focus liquid microlens array using dielectrophoretic effect.

A tunable-focus liquid microlens array based on dielectrophoretic effect was demonstrated. In a lens cell, two immiscible dielectric liquids but with different dielectric constants are sandwiched between electrodes. One electrode has a holed pattern while the other electrode is continuous. The applied voltage generates an inhomogeneous electric field near the hole regions. Owing to such an electric field, the generated dielectric force would separate the low dielectric liquid into many pieces and each piece is pushed to its neighboring hole. After balance, the droplet array is formed in the contracting state surrounded by the high dielectric constant liquid. Each droplet exhibits a lens character. When the voltage is removed, the droplets relax slightly but still keep a certain contact angle. Reactivating the cell will again enforce the droplets to reshape from relaxing to contracting states and, therefore, changing the focal length. Such a lens cell can be fabricated easily and its response time is reasonably fast. Its potential applications in image processing and zoom lens are emphasized.