A polymeric microporous filtration membrane comprising: (a) a first microporous surface; (b) a second microporous surface; and (c) a bulk between the first surface and the second surface; wherein the bulk comprises a first porous portion including the first microporous surface, and a second porous portion including the second microporous surface; and (i) the first porous portion comprises at least first and second sets of different controlled pore structures, the first set of controlled pore structures comprising channels having an aspect ratio of at least 4, a diameter ranging from 4 μm to 40 μm and a length in the range of from 39 μm to 140 μm; said second set of controlled pore structures having an average pore size in the range of about 0.5 μm to about 10 μm; said first porous portion comprises at least one additional set of controlled pore structures, the additional set having a smaller average pore size than the second set in the range of 0.3 μm to 5 μm; and (ii) the second porous portion comprises a third set of a controlled pore structures, wherein the third set of pore structures has a smaller average pore size than the second set of controlled pore structure, wherein the membrane has a thickness of from 70 μm to 400 μm; and wherein the membrane comprises at least first and second layers integrally bonded to one another, the first layer comprising the first porous portion with said first microporous surface, said first porous portion having a thickness in the range from 25% to 80% of the total thickness of the layer, and the second layer comprising the second porous portion with the second microporous surface. (a) a first microporous surface; (b) a second microporous surface; and (c) a bulk between the first surface and the second surface; wherein the bulk comprises a first porous portion including the first microporous surface, and a second porous portion including the second microporous surface; and (i) the first porous portion comprises at least first and second sets of different controlled pore structures, the first set of controlled pore structures comprising channels having an aspect ratio of at least 4, a diameter ranging from 4 μm to 40 μm and a length in the range of from 39 μm to 140 μm; said second set of controlled pore structures having an average pore size in the range of about 0.5 μm to about 10 μm; said first porous portion comprises at least one additional set of controlled pore structures, the additional set having a smaller average pore size than the second set in the range of 0.3 μm to 5 μm; and (ii) the second porous portion comprises a third set of a controlled pore structures, wherein the third set of pore structures has a smaller average pore size than the second set of controlled pore structure, (i) the first porous portion comprises at least first and second sets of different controlled pore structures, the first set of controlled pore structures comprising channels having an aspect ratio of at least 4, a diameter ranging from 4 μm to 40 μm and a length in the range of from 39 μm to 140 μm; said second set of controlled pore structures having an average pore size in the range of about 0.5 μm to about 10 μm; said first porous portion comprises at least one additional set of controlled pore structures, the additional set having a smaller average pore size than the second set in the range of 0.3 μm to 5 μm; and (ii) the second porous portion comprises a third set of a controlled pore structures, wherein the third set of pore structures has a smaller average pore size than the second set of controlled pore structure,