Patent ID: 7354392

Claim:
A filter device for being implanted in a blood vessel for carrying out in-vivo plasma separation comprising: a plurality of elongated hollow tubes comprising one or more first and one or more second elongated hollow tubes, and a plurality of elongated fibers each fiber having a microporous membrane fiber wall with an outer wall surface and an inner wall surface defining an interior lumen extending along the length thereof wherein the fiber wall morphology of each of the elongated fibers is asymmetrical between the inner wall surface and the outer wall surface, said fiber wall having a higher mass density zone adjacent to the outer wall surface and a lower mass density zone adjacent to the inner wall surface, said higher mass density zone having a smaller average nominal pore size than the average nominal pore size in the lower mass density zone, each fiber having a first end secured to a first said elongated hollow tube and a second end secured to a second said elongated hollow tube, wherein the interior of the said plurality of elongated hollow tubes communicates with the interior lumen of each of the fibers, said fibers including one or more continuous filaments embedded in the microporous fiber wall between the first and second ends of the fiber.