Electrically templated dewetting of a UV-curable prepolymer film for the fabrication of a concave microlens array with well-defined curvature

This paper presents an economic method, based on electrically templated dewetting of a UV-curable prepolymer, for fabricating a concave microlens array (MLA) of high quality and high density. In our strategy, a voltage is applied to an electrode pair consisting of a conductive substrate coated with a UV-curable prepolymer film and a microhole-arrayed silicon template, sandwiching an air gap, to dewet the prepolymer film into a curved air-liquid interface. At or beyond a critical voltage, the curved prepolymer can be pulled quickly into contact with the protrusive underside of the silicon template. Contact of the prepolymer with the template can be detected by monitoring the leaky current in the polymer, followed by a UV curing of the prepolymer. Finally, by separating the mold from the solidified polymer, a concave MLA is obtained. The curvature of the MLA can be well-defined simply by changing the air gap between the mold and prepolymer film. Besides, the dewetting strategy results in a much smaller adhesion area between the mold and solidified polymer structures, which allows for easy separation of the mold from the MLA in a large-area operation.