Porous polymeric membrane with tear prevention ring

A method for making a tear-resistant liquid-filtering porous membrane comprising:

• a) depositing a photoresist layer on the top surface of a substrate, the substrate comprising a support layer, a polymer layer, and a hard mask layer;
• b) exposing the photoresist to a pattern of light;
• c) developing the photoresist layer to provide a first pattern of openings in the photoresist layer that expose portions of the hard mask layer;
• d) etching the exposed portions of the hard mask layer to provide a second pattern of openings in the hard mask layer that expose portions of the underlying polymer layer;
• e) removing the photoresist;
• f) etching the polymer layer through the second pattern of openings in the hard mask layer thereby providing a third pattern of openings in the polymer layer, the third pattern of openings including a pore region and a segmentation region surrounding the pore region with a tear-resistant boundary region between the pore-region and the segmentation region, the pore region comprising a plurality of pores having a minimum dimension of less than 100 microns;
• g) removing the hard mask layer;
• and,
• h) releasing the polymer layer from the substrate, thereby providing the tear- resistant liquid-filtering porous membrane, wherein the pore region and the tear-resistant boundary region are defined by the pattern of light.