A cartridge for use in flow filtration, comprising:
- (a) a housing having a housing interior, a first end, a second end, and a housing body extending from the housing first end to the housing second end, wherein the housing first end includes a dialysate inlet, the housing second end includes a dialysate outlet, the housing body includes a blood inlet and a blood outlet;
- (b) a plurality of fibers contained inside said housing in the housing interior, wherein:
- (i) said plurality of fibers comprising a mixture of polyethersulfone and polyvinylpyrrolidone;
- (ii) at least some of said plurality of fibers being hollow and being made of semi-permeable membranes having respective fiber interiors and fiber exteriors
- (iii) the fiber exteriors being smoother than the fiber interiors;
- (iv) said plurality of fibers being parallel or almost parallel to each other over at least a substantial portion of their lengths;
- (v) said plurality of fibers having a porosity in an inter fiber space of between 40% and 70%;
- (vi) said fiber exteriors have a hemocompatible exterior surface wherein the hemocompatible exterior surface is wettable by water without substantial hydrophobic patches;
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- (vii) said fiber exteriors have a root-mean-square surface roughness of less than 100 nanometers;
- (c) a first end barrier that joins with said plurality of fibers at first ends of said plurality of fibers and joins with said housing interior and bounds a first end plenum and separates said first end plenum from a housing midsection interior region;
- (d) a second end barrier that joins with said plurality of fibers at second ends of said plurality of fibers and joins with said housing interior and bounds a second end plenum and separates said second end plenum from said housing midsection interior region;
- (e) a first fluid flow compartment comprising said first end plenum and said fiber interiors and said second end plenum, said first end plenum and said fiber interiors and said second end plenum being in fluid communication with each other;
- (f) a second fluid flow compartment comprising the interfiber space and the blood inlet and the blood outlet, all in fluid communication with each other, wherein said second fluid flow compartment comprises a supply distributor inside said housing near said blood inlet, and a discharge distributor inside said housing near said blood outlet, wherein said supply distributor and said discharge distributor are each constructed to introduce or discharge blood to or from said fiber exteriors substantially 360 degrees around a circumference of said plurality of fibers to create uniform or quasi uniform blood flow in the inter fiber space;
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- (g) wherein near said supply distributor said plurality of fibers fan having a supply end fanning angle, and near said discharge distributor said plurality of fibers have a discharge fanning angle that is smaller than the supply end fanning angle.