Adsorption control of synovia constituents on artificial joint materials by means of an electric field: evaluation of tribological characteristics

The supplemental lubrication mechanism by means of an electric field was proposed to reduce friction and wear for the advanced joint prosthesis with the low elastic modulus bearing surface. The possibility of application of this mechanism to the prosthesis was investigated by the fundamental and experimental procedures in simplified sliding conditions. Conductive silicon rubber was used as the low elastic modulus surface. The counterfaces were a titanium alloy and a stainless steel. Protein (gamma-globulin) in lubricant appeared to cause the tribological characteristic to deteriorate in the mixed lubrication regime. High friction seemed to be brought about by the obstruction against the entraining of the fluid flow and the high shear stress due to the microbonding between the asperities of bearing surfaces, which were derived from the adsorbed protein on the hydrophobic surfaces. The repulsive force between the adsorbed film and the bearing materials by means of the d.c. electric field, and the continuous change in polarity on the surface by means of the a.c. electric field appeared to affect the adsorbed film adjacent to the bearing material, so that friction and wear were varied.