end use of the membrane in the exemplary embodiment membrane substrate 12 is made from polytetrafluoroethylene ptfe film that has been expanded to form an open pore structured membrane known as expanded polytetrafluoroethylene eptfe in alternate embodiments woven polytetrafluoroethylene and non woven polytetrafluoroethylene are used to make membrane substrate 12 other materials and methods can be used to form a suitable base membrane substrate 12 that has an open pore structure for example other suitable materials include but are not limited to polyolefin polyamide polyester polysulfone polyether acrylic and methacrylic polymers polystyrene polyurethane polypropylene polyethylene and caco 3 filled polyethylene other suitable methods of making a porous membrane include foaming skiving or casting any of the suitable materials fig3 is a cross sectional schematic illustration of another exemplary embodiment of an asymmetric porous membrane 50 that includes a first base membrane substrate 52 and a second base membrane substrate 54 bonded together the bonding may be done using any known appropriate adhesive or thermal lamination process that enables asymmetric porous membrane 50 to function as described herein first membrane substrate 52 has a first side 56 and an opposing second side 58 second membrane substrate 54 has a first side 60 and a second side 62 second side 58 of first membrane substrate is bonded to first side 60 of second membrane substrate 54 with an adhesive 64 or any other appropriate lamination process first and second membrane substrates.