We have found that micro porous polymer films were prepared by simple casting of polymer solution under humid atmospheric condition when water-immiscible organic solvent was used as evaporating solvent. Mono-dispersed water droplets are formed on the surface of the casting polymer solution by water condensation due to evaporation cooling. A surface monolayer of the self-packed water droplets formed on the polymer solution surface acts as a temporary template of micropores. Honeycomb-like hexagonally packed regular-sized micro-pores were formed in the polymer film after evaporation of solvent and water. Biomedical application is an emerging requirement for the honeycomb-patterned polymer flms, especially of biodegradable polymers. Hepatocytes cultured on the honeycomb-patterned film formed spheroid expressing liver functionality, e.g. albumin secretion. The shapes and function of the liver cells can be regulated by the pore size of the honeycomb film. Spheroid aggregates were also formed from neural stem cells on the honeycomb-patterned film.
