Variable focus dielectric liquid droplet lens

A liquid crystal droplet lens driven by the dielectrophoresis (DEP) force was demonstrated. The liquid crystal droplet lens was deformed by the DEP forces under non-uniform AC electric fields. Focal length, hysteresis and electrode design were studied. The focal length varied from 1.6mm to 2.6mm in the range of 0-200V at 1 kHz for electrode spacing of 50 mu m; that is, the tuning ratio of the focal length was about 60% in maximum. The hysteresis of contact angle was found to be less than 3 and it vanished after 1 minute at the rest state. As the electrode spacing over 200 mu m, the tuning ratios of the focal length dropped below 5%. The liquid crystal droplet lens that had numerical aperture of about 0.5 consumed power of about 0.1mW. Its response time was measured to be about 220ms. (c) 2006 Optical Society of America