A peer-reviewed study introduced deep-foam photolithography, which forms pores throughout photosensitive polymers. UV-A light, a solvent and controlled collapse formed white and greyscale structures without pigment or ink at resolutions reaching 20,000 dots per inch. The method worked on films and fibres and was also adapted to water-repellent surfaces and microfluidic structures.
Researchers sent UV-A light through the depth of a photosensitized polymer film rather than treating only its surface. The light split and crosslinked polymer chains, after which a weak solvent initiated pores throughout the film. Controlled collapse of those pores as the solvent was removed created the hierarchical microstructure the team calls deep-foam photolithography.[1], [2]
Irregular pores inside the foam scattered light to create a white appearance without pigment or ink. Altering pore size and distribution also allowed greyscale printing. In the peer-reviewed experiments, pattern resolution reached 20,000 dots per inch. The colour arose from the structure's interaction with light rather than a chemical dye, The process combined printing with the material's physical architecture.[1], [2]
Controlled collapse also formed water-repellent surfaces with hierarchical roughness resembling a lotus leaf. The method worked in amorphous and semi-crystalline polymers and on fibres as well as flat films. By patterning foamability and wettability at micrometre scale, researchers made microfluidic channels and structures that captured picolitre liquid droplets. These are laboratory demonstrations; performance in large-scale manufacturing has not yet been established.[1], [2]
