Fluidic lenses with variable focal length

We demonstrate in this letter that variable focus lenses can be realized by pressure-induced deformation of a liquid interface. Large deflections can be achieved by exploiting the capillary pressure barrier generated by high surface tension liquids at the exit of a small well. Modulation of the internal pressure of a liquid interface produces a change in its radius of curvature thus a shift in the plane of focus. Using liquids with high surface tension like water and polymeric low surface energy substrates, liquid-air lenses were realized with a wide focal length tunability (optical power for 2 mm lenses from 130 to 350 diopters). Using the liquid-liquid interface of water and a nonmiscible liquid, pressure-induced tunable lenses were also demonstrated. The application of the lenses in imaging was also shown.