The invention concerns the use of an asymmetric porous membrane for the evenly distributed concentration of a substance which is not or not substantially adsorbed to the membrane and which is brought into contact with the membrane in the form of a membrane-wetting solution on the fine-pored side of the...http://www.google.com.tw/patents/US6287867?utm_source=gb-gplus-share專利 US6287867 - Asymmetric porous membranes
