Effect of annealing on structure and biomedical properties of amorphous hydrogenated carbon films

The usual failure of blood-contacting biomedical materials and devices arises from thrombogenesis. When a biomaterial comes in contact with a biological body, interface interaction will be concomitant between the biomaterial surface and biological substance, such as blood protein denaturation resulting from electrical charge transfer of proteins and platelet activation induced by interface thermodynamics. Diamond-like carbon (DLC) has been proposed for use in blood contacting devices. Further understanding of the intrinsic relationship between biomedical properties and structure of amorphous carbon films will promote improvement of their biocompatibility. In this study, hydrogenated amorphous carbon (a-C:H) films were fabricated at room temperature using plasma immersion ion implantation-deposition (PIII-D). A series of a-C:H films with different structures and chemical bonds were obtained by adjusting the DC bias voltage from −75 to −900 V, then their structure and physical properties were further modified by thermal anneal in vacuum at 600 °C. Raman, elastic recoil detection (ERD) and atomic force microscope (AFM) were used to characterize their structures and chemical bonds. The physical properties and surface characteristics of the films were also examined, including the carrier concentration and mobility, resistivity, and surface wettability. The anticoagulation of the films was evaluated employing in vitro platelet adhesion test. The adhesion, activation, and morphology of the platelets were investigated using scanning electron microscopy (SEM). The relationship between their structure and blood compatibility was elucidated.