Low Cost Fabrication of Micro- and Nanopores in Free-Standing Polymer Membranes for Study of Lipid Adsorption

This study presents low cost fabrication of free-standing membranes in polymer with perforated pores down to subμm diameter, which provides platforms for fundamental studies of many biosystems. For the fabrication, a combination of imprint lithography and a sacrificial layer technique was employed in order to obtain a clean, fully released, and mechanically stable membrane with perforated pores. Lift-off resist (LOR) was used as a sacrificial layer first while SU-8 resist spin-coated on the LOR layer was used as the active membrane layer in which microand nanopores patterns are formed via a combined thermaland UV-imprint process. With this method, we could achieve a large area, free-standing SU-8 membrane with micropores up to 4 inch diameter. As a demonstration of the use of the membrane in the study of a biosystem, the membrane was exposed to a solution with lipid vesicles. Lipid vesicles preferentially adsorb at the pore sites in the membrane, the extent of which depends on a surface treatment with poly(L-lysine)graft-poly(ethylene glycol) (PLL-g-PEG) performed prior to the lipid adsorption. We will also show integration of the polymer membrane into microfluidic devices made of polydimethysiloxan, which allows for in-situ study of lipid adsorption.