Functionalization of hydrogen-free diamond-like carbon films using open-air dielectric barrier discharge atmospheric plasma treatments

Abstract

A dielectric barrier discharge (DBD) technique has been employed to produce uniform atmospheric plasmas of He and N 2 gas mixtures in open air in order to functionalize the surface of filtered-arc deposited hydrogen-free diamond-like carbon (DLC) films. XPS measurements were carried out on both untreated and He/N 2 DBD plasma treated DLC surfaces. Chemical states of the C 1s and N 1s peaks were collected and used to characterize the surface bonds. Contact angle measurements were also used to record the short-and long-term variations in wettability of treated and untreated DLC.In addition, cell viability tests were performed to determine the influence of various He/N 2 atmospheric plasma treatments on the attachment of osteoblast MC3T3 cells.Current evidence shows the feasibility of atmospheric plasmas in producing long-lasting variations in the surface bonding and surface energy of hydrogen-free DLC and consequently the potential for this technique in the functionalization of DLC coated devices. IntroductionIn a recent study it was shown that the nanoscale wettability of a hydrogenterminated diamond surface was lower than that of regions that had been oxidized using an atomic force microscope tip [1]. The difference in wettability between modified diamond surfaces suggests the application of control wettability of modified carbon surfaces in the fields of medicine and biotechnology, which could also be extended to diamond-like carbon films.Diamond-like carbon (DLC) films are known to be hard, low friction and chemically inert materials. Numerous in-vitro and in-vivo experiments have indicated that DLC can have both excellent biocompatibility and hemocompatibility [2][3][4][5]. In the past, the wettability of DLC coatings has been modified by selective doping using both metal and non-metal dopants [6][7][8]. For instance, both silicon and fluorine can be used to increase the surface energy and reduce the contact angle with water. In one study [6], researchers modified the surface energy of DLC by incorporating oxygen and silicon into the bonding network, thus avoiding the use of harmful fluorine-containing hydrocarbon gases. However, the silicon-containing DLC coatings had 20 times lower wear resistance than undoped DLC films. In other recent study [9], phosphorus-doped DLC films were deposited by applying hybrid plasma immersion ion implantation and deposition (PIIID) techniques; the good wettability exhibited by P-doped DLC samples leads to an increase in hemocompatibility. However, in this study the mechanical properties of the modified films were not analyzed. In a different study [5], substrates with various substrate roughness were employed to investigate the attachment of human osteoblast cells to amorphous carbon films with different surface textures. This study concluded that cell attachment increased monotonically with surface roughness. However, smooth surfaces are critical in the vast majority of biomedical applications and topological functionalization of the surface cannot be seen as a wide-rang...

60 years of DLC coatings: Historical highlights and technical review of cathodic arc processes to synthesize various DLC types, and their evolution for industrial applications

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Characterization of physical and biomedical properties of nitrogenated diamond-like carbon films coated on polytetrafluoroethylene substrates

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Effects of plasma surface treatments of diamond-like carbon and polymeric substrata on the cellular behavior of human fibroblasts

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