Self-detached membranes with well-defined pore size, shape and distribution fabricated by underexposure photolithography

Abstract

An underexposure photolithography method was developed to fabricate self-detached polymer micropore membranes with uniform pore size, shape, and arrangement. The key to this technique is to control and adjust the gradient of exposure dose projected into the film of photoresist. This new approach abandons sacrificial layers used in previous techniques. Negative SU-8 was chosen as an example photoresist to demonstrate its feasibility. Membranes with specially tailored sizes and shapes of micropores could be produced on diverse substrates. The coefficient of variation of pore size was only 1%, much lower than that for conventional microporous membranes. Moreover, due to self-detaching without a sacrificial layer, the membranes were flat and free of residual stress and deformation. This novel photolithographic approach opened a new avenue to manufacture high-quality membranes that could broaden the applications of microparticle filtration, separation, and sorting.