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.