Leveraging polymerization shrinkage in thin films for microlens array fabrication

Microlens arrays have diverse applications in imaging, illumination, sensing and communication. However, their fabrication poses significant challenges due to strict optical uniformity requirements across thousands of lenslets. Direct methods based on surface tension provide high-quality lenslets but have a limited NA range and rely on surface chemistry, which impairs their uniformity. Mold-based approaches produced by machining are more flexible but yield lower surface quality and are cost effective only for large volume production. We here present a novel approach for fabrication of high quality microlens array molds that leverages the interplay of surface tension and polymer shrinkage in thin liquid films. We demonstrate the creation of an array of 100 um diameter lenslets with an average regularity of 37nm RMS across 449 lenslets, and surface roughness of less than 1nm. The entire process requires minutes to complete and can be useful both for prototyping and mass manufacturing applications.