Ultra-hydrophilic Diamond-like Carbon Coating on an Inner Surface of a Small-diameter Long Tube with an Amino Group by AC High-voltage Plasma Discharge

Medical tubing includes artificial vascular grafts and catheters, each has a different purpose of use, but they both need to hydrophilize the lumen surface. Diamond-like carbon (DLC) is a dry coating technology, and its surface can be easily modified with hydrophilic functional groups. AC high-voltage plasma chemical vapor deposition has been developed for DLC deposition on the inner surface of small-diameter long tubes. In addition, oxygen plasma treatment of the DLC-deposited surface has been performed to enhance the hydrophilicity of the tube lumen and to inhibit biofilm adhesion in urinary catheters. However, the oxygen plasma treatment using silicone as the base material had only a slight inhibitory effect on biofilm adhesion, with a water contact angle of 104.4° for the DLC film and 90.6° for the DLC film, compared with oxygen plasma treatment, with an average value of 119.5° for the blank film. Recently, a new ammonia plasma treatment method has been developed, and an ultra-hydrophilic water contact angle of nearly 10° has been achieved with polyurethan (PU) as the base material. Furthermore, the zeta potential was found to be negative in oxygen plasma treatment and positive in ammonia plasma treatment, indicating that the hydrophilicity, and surface potential can be arbitrarily controlled by combining these plasmas, thereby achieving surface properties suitable for various applications.