The present invention involves porous polymer membranes, suitable for use in medical implants, having controlled pore sizes, pore densities and mechanical properties. Methods of manufacturing such porous membranes are described in which a continuous fiber of polymer is extruded through a reciprocating extrusion head and deposited onto a substrate in a predetermined pattern. When cured, the polymeric material forms a stable, porous membrane suitable for a variety of applications, including reducing emboli release during and after stent delivery, and providing a source for release of bioactive substances to a vessel or organ and surrounding tissue.