Patent ID: 7201846

Claim:
A method for making an anti-microbial filter for a micro-fluidic system, the method comprising the steps of: providing a substrate; forming a filter membrane of a filter material on the substrate; and forming a plurality of holes through the filter membrane by providing a filter mask having a plurality of holes therein over the filter membrane by depositing a plurality of spacers on the filter material such that a part of each of the spacers contacts the filter material to define said plurality holes in the filter mask, depositing filter mask material partially around the spacers and on the filter material such that the part of each of the spacers that contacts the surface of the filter material prevents the filter mask material from continuously coming between the spacers and the filter material and thereby defines one of the plurality of holes in the filter mask, removing the plurality of spacers to form the plurality of holes in the filter mask, and forming the plurality of holes in the filter membrane in registration with the plurality of holes in the filter mask; and removing at least a portion of the substrate to expose at least some of the holes in the filter membrane; wherein, said spacers are sub-micron particles selected from polystyrene, silica or carboxylate polystyrene.