Cross flow microfilter

In a cross flow microfilter comprising a filter housing having a flow chamber wherein a fluid is introduced through at least one inlet and a concentrate is removed through at least one outlet on the side opposite the inlet, a collection chamber from which a filtrate is removed, and at least one microporous membrane disposed between the flow chamber and the collection chamber, said membrane having an inlet surface along which the fluid to be filtered flows, an outlet surface oriented toward the collection chamber and pores of a width between about 0.1 micron and 30 microns, the improvement wherein

• said membrane comprises a plurality of webs disposed in at least one row and spaced at a predetermined distance from one another to define openings having slit-shaped cross-sections said openings having uniform and predetermined widths and given profiles and constituting said pores;
• said microfilter further comprises two terminating plates enclosing said webs and laterally bounding said openings;
• and
• said webs are formed on one of said plates by one of X-ray lithography, X-ray depth lithographic-galvanoplasty molding, and molding with subsequent galvanoplasty.