Abstract: A membrane is provided, comprising a first membrane layer having a first side and a second side. The first membrane layer defines a plurality of holes extending along a first axis between the first side and the second side. Each hole is defined by the first membrane layer as a complex three-dimensional shape, and each hole has a diameter of less than about 10 micrometers. The membrane is fabricated by dispersing a liquid polymeric material onto a patterned master template, hardening the polymeric material, and removing it from the master template. The membrane includes through holes which correspond to the structures of the patterned master template in size, cross-sectional and three dimensional shape, orientation, and the like.