Polymeric microlens array fabricated with PDMS mold-based hot embossing

Abstract

This study presents a simple, flexible and cost-effective process to fabricate microlens arrays. The polymeric microlens arrays are fabricated using a polydimethylsiloxane (PDMS) mold-based hot embossing process. The desired profile of the lens is achieved with the use of air pressure to deform the PDMS membrane. The deformation of the PDMS membrane is determined by numerical simulation. Simulation results show that the sag height of the PDMS membrane varies nearly linearly along with the change of the negative pressure. The shape of the PDMS membrane is transferred to the PDMS mold with UV curing and casting processes. Then, PDMS is used as a mold insert, and polycarbonate microlens arrays with different sag heights are fabricated with the hot embossing technique. The surface profile of the fabricated microlens keeps spherical with the variation of the sag height induced by the negative pressure. For the negative pressure −3600 and −5900 Pa, sag heights with 40 and 65 µm are obtained and the corresponding focal lengths are changed from 1.0 to 0.6 mm. Good uniformity and imaging quality of the microlenses is confirmed by the experimentally evaluated and measured optical properties of the replica.