Evaluation of sliding properties and durability of DLC coating for medical devices

Metallic materials that are used in medical devices such as SUS and brass generate friction against biological tissue. Therefore, when a device is inserted into the body, the patient may feel invaded and uncomfortable because of the friction. In addition, medical devices must be sterilized after use, and the devices may deteriorate with sterilization. Diamond-like carbon (DLC), which possesses advantageous characteristics such as a low friction coefficient, biocompatibility, and chemical stability, has attracted attention as a surface-modification material for medical devices. In this study, the biological characteristics and durability of DLC/SUS samples formed on SUS substrates by the ionized vapor deposition method were evaluated. From the results of friction-coefficient measurements performed with the ball-on-disc test, the friction coefficient was reduced by factors of approximately 1/4 and 1/5 through DLC coating under atmospheric dry conditions (Dry) and in a physiological saline solution (Wet), respectively. The durability of DLC was evaluated by immersion in an acidic solution. Furthermore, the durability against sterilization treatment was tested using an autoclave. The usefulness of DLC coating was confirmed from the results of observing the surface smoothness of the sample after immersion in an acidic solution and sterilization treatment. The above results suggest that DLC film coating is a useful technique for improving the surfaces of medical devices.