Patent ID: 8714722

Claim:
A structure, comprising: filter assembly, comprising: a first filter layer comprising a plurality of pores therein arranged in a pattern, wherein the plurality of pores in the first filter layer comprises a first pore pitch; a second filter layer adjacent to the first filter layer and comprising a plurality of pores therein arranged in a pattern, wherein the plurality of pores in the second filter layer comprises a second pore pitch which is different than the first pore pitch; and a fluid path through the filter assembly, wherein an area of overlap of the pores in the first filter layer with the pores in the second filter layer, in a vertical direction perpendicular to a plane of the filter assembly, comprises a periodicity defined by the area of overlap of each pore in the first filter layer with one of the pores in the second filter layer across the filter assembly; wherein: each of the plurality of pores in the first filter layer comprises a taper, wherein a first pore opening at a first surface of the first filter layer is larger than a second pore opening at a second surface of the first filter layer; each of the plurality of pores in the second filter layer comprises a taper, wherein a first pore opening at a first surface of the second filter layer is larger than a second pore opening at a second surface of the second filter layer; and the plurality of pore openings in the second surface of the first filter layer faces the plurality of pore openings in the second surface of the second filter layer.