Focal-length-tunable elastomer-based liquid-filled plano-convex mini lens

A liquid plano-convex lens with focal length tuning is proposed, which is formed by sinking an oil droplet onto the bottom of an elastomer. A simple and low-cost fabrication method is presented. The lens aperture and initial focal length can be controlled during the fabrication. Furthermore, focal length tuning is demonstrated. The lens made of a 40 mg oil droplet can achieve the tuning range from 12 to 17 mm. The effective aperture of the lens is about 2.8 mm. In the demonstration of an imaging system, the lens assists in focusing and a clear image can be observed.