Method of forming implantable vascular grafts

Claim 1

A method of forming biocompatible vascular graft, comprising: extruding a continuous fiber forming biocompatible polymeric material through an orifice in order to form an elongated fiber; winding said elongated fiber on a mandrel such that the continuous fiber forms a plurality of windings that define a non-woven cylinder having overlying fibers that contact one another; intermittently applying an electrostatic charge between said extrusion orifice and said mandrel, said intermittent electrostatic force application procedure including accelerating the elongated fiber onto the mandrel by applying the electrostatic charge between the extrusion orifice and the mandrel after a time period when said winding is carried out in the absence of the electrostatic charge; at least a portion of said winding procedure that is carried out on at least certain outer ones of said plurality of windings is carried out in the absence of said electrostatic charge after a time period when said winding is carried out under the influence of the electrostatic charge between the extrusion orifice and the mandrel in order to form a substantially porous outer surface that is conducive to tissue ingrowth thereinto after the vascular graft is implanted; observing breakage of the continuous fiber during said winding procedure and applying the electrostatic charge as soon as possible after such breakage occurs for the purpose of accelerating the broken fiber toward the mandrel to reattach the free end to the graft and ceasing to apply such electrostatic charge once such reattachment has been accomplished; and removing said non-woven cylinder from said mandrel to provide said biocompatible vascular graft.

Claim 2

A method of forming biocompatible vascular graft, comprising: extruding a continuous fiber forming biocompatible polymeric material through an orifice in order to form an elongated fiber; winding said elongated fiber on a mandrel such that the continuous fiber forms a plurality of windings that define a non-woven cylinder having overlying fibers that contact one another; intermittently applying an electrostatic charge between said extrusion orifice and said mandrel, said intermittent electrostatic force application procedure including accelerating the elongated fiber onto the mandrel by applying the electrostatic charge between the extrusion orifice and the mandrel after a time period when said winding is carried out in the absence of the electrostatic charge; at least a portion of said winding procedure that is carried out on at least certain outer ones of said plurality of windings is carried out in the absence of said electrostatic charge after a time period when said winding is carried out under the influence of the electrostatic charge between the extrusion orifice and the mandrel in order to form a substantially porous outer surface that is conducive to tissue ingrowth thereinto after the vascular graft is implanted; observing breakage of the continuous fiber during said winding procedure and applying the electrostatic charge as soon as possible after such breakage occurs for the purpose of accelerating the broken fiber toward the mandrel to reattach the free end to the graft and ceasing to apply such electrostatic charge once such reattachment has been accomplished; and removing said non-woven cylinder from said mandrel to provide said biocompatible vascular graft.