Plasma-induced shaping of liquid-based polymer lenses

Liquid-based lenses are of notable interest for the realization of prototypes, small batch series and even mass-product articles as for example micro lens arrays or low-cost optics. Hence, quite a number of different approaches for the manufacture of such lenses are in hand. The focal length of liquid lenses can be customized by the choice of the used liquid, a modification of its viscosity, for example via heating, substrate coating or overhead storing and curing. In this contribution, we present a further approach based on plasma treatment of the substrate surface where two different effects are generated by the use of different process gases. After treatment, optical cement is applied to the surfaces, forming a plano-convex lens due to surface tension. Argon plasma treatment leads to a reduction of the contact angle and an increase in the focal length of the lens in the course of treatment. The opposite effect, an increase in contact angle and a decrease in focal length, respectively, occurs when using octafluorocyclobutane as process gas. The possible range of currently realizable focal lengths and the particularly underlying effects are presented in this contribution.