Tuning C-C sp2/sp3 ratio of DLC films in FCVA system for biomedical application

Diamond like carbon(DLC)films with different C-C sp2/sp3 ratios were prepared by tuning the N2 flow rate in a filtered cathodic vacuum arc(FCVA)system.The increase of N2 flow rate facilitated the increase of C-C sp2/sp3 ratio(1.09-2.66),the growth of particle size(0.78-1.58 nm)and the improvement of surface roughness.The SBF immersion results,as well as WCAs(77.57°~71.71°),hemolysis rate(0.14-1.00%)and cytotoxicity level(0)demonstrated that the as-fabricated DLC film was promising for biomedical application.As a result of surface charge effect,the apatite layers formed in the SBF increased with the increase of C-C sp2/sp3 ratio until 1.74 and then showed a tiny decrease during 1.74-2.66.A raise of hemolysis and cytotoxicity was observed when sp2/sp3 ratio was increased.Moreover,a decrease of friction coefficient of Si surface induced by increasing sp2/sp3 ratio was respectively evidenced in ambient air and SBF lubrication environments.