Shear Strength of Protein Film Formed by Friction of SiC/SiC Sliding Pair in Plasma Environment

This study aimed to clarify the shear strength of a protein film formed by friction of a SiC/SiC sliding pair in a plasma environment. A ball/disk-type tribometer was utilised to obtain the relationship between the friction force in the plasma and the area of protein aggregates formed on the textured SiC disk sliding against the SiC ball in the plasma. To control the area of protein aggregates adsorbed onto the SiC disk surface, different surface textures and ultraviolet (UV) irradiation for the SiC disk were introduced based on past research. Protein aggregates formed owing to protein denaturation and were adsorbed onto the fabricated surface texture of the SiC disk. A broad protein film formed on the SiC disk surface through conjugation of multiple protein films formed from closely distributed concaves. Therefore, the distribution of fabricated concaves determines the conjugation of the protein film formed from each concave, and the trends of frictional force for each SiC/SiC frictional pair in the plasma depends on the area of protein aggregates. In other words, the area of protein aggregates and the frictional force show an almost linear relationship, regardless of the surface texture on the SiC disk or UV irradiation. Finally, the shear strength of the protein aggregates against the sliding SiC ball in plasma was 7.14 MPa, as determined from the relationship between the area of the protein aggregates and the frictional force in the plasma environment.