Methods of Soft PDMS Microlens Arrays Fabrication via Air-Expansion-Induced Molding with 3D-Printed Templates

Conventional methods for microlens array (MLA) fabrication suffer from high costs, long prototyping time, and limited geometric control. To address these problems, this study introduces an air-expansion-induced molding method for soft lens array fabrication. This method works by heating the air trapped in 3D-printed photoresist microcavities. The photoresist becomes convex due to the thermal expansion of the trapped air and is then solidified after UV curing as a mold for Polydimethylsiloxane (PDMS) casting. The deformation of the photoresist is theoretically analyzed and experimentally verified. It is found that the fabricated MLAs exhibit sub-10 nm surface roughness and their curvature scales with both microcavity depth and temperature. The MLAs achieve an imaging resolution of 228.1 line pairs per millimeter and enable multi-focal plane imaging of microalgae in a microfluidic chip.