Novel DLC coating technique on an inner-wall of extended polytetrafluoroethylene vascular grafts using methane plasma produced by AC HV discharge

Expanded-polytetrafluoroethylene (ePTFE) generally exhibits good compatibility with blood in the form of a vascular graft material; however, the small diameter grafts exhibit a low patency rate. ePTFE, with a diameter of less than 6 mm, is usually not used to perform a bypass surgery because of its high occlusion rate due to thrombosis or thick neointimal formation. Therefore, to improve the patency rate of ePTFE, coating the inner surface of ePTFE using Diamond-like Carbon (DLC), which exhibits outstanding biocompatibility, is investigated. However, in reality, medical applications for a long-sized tube that has a diameter of less than 6 mm with a DLC-coated inner wall are scarce. Hence, in this study, AC high-voltage methane plasma Chemical Vapor Deposition is employed to form the bio-compatibilized inner wall of a small-diameter long-sized medical tube, and a Hydrogenated Amorphous Carbon (a-C:H) deposition technique is developed. Further, methane plasma discharge is confirmed to be confined within the ePTFE vascular graft tube (inner diameter of 4 mm and an overall length of 150 mm) with the inner wall being successfully coated by the a-C:H film.