The Adsorption Of Biomolecules And Effects On Tribological Behavior Of Carbon-like Film

Carbon-like films are considered to be the most potential surface-modification inorganic materials for artificial joints,since they offer superior resistance to wear,corrosion and excellent biocompatibility.When the modifided artificial joints serve in human body,molecules from the synovial fluid or periprosthetic fluid will be adsorbed on the carbon-like film.This will affect the tribological behavior of joints,and even affect the lifetime of artificial joints.Therefore,it is meaningful to investigate the tribological mechanism of carbon-like film in synovial fluid,and find out the effects of main component?albumin,?-globulin and hyaluronic acid?in synovial fluid.This will help to increase the resistance to wear,corrosion of the carbon-like film and extend the lifetime of artificial jonits.In this study,hydrogen free carbon-like film?a-C?and hydrogenated carbon-like film?a-C:H?were prepared on CoCrMo alloy substrate by filtered cathodic vacuum arc?FCVA?and microwave electron cycoltron resonance-plasma enhanced chemical vapor deposition?ECR-PECVD?,respectively.We also prepared a-C and a-C:H on piezoelectric quartz crystals for albumin?BSA?,?-globulin?HGG?and hyaluronic acid?HA?molecules adsorption test,and the adsorption of the three molecules were studied.The effect of adsorption on the tribological behavior of carbon-like film were studied further with open circuit potential.The results of adsorption show that on the a-C film surface,BSA molecules form a monolayer film with side-on orientation,HGG molecules form a monolayer film with end-on orientation,and HA molecules cannot be adsorbed.The results of competitive adsorptions show that HGG molecules can displace the pre-adsorbed BSA molecules,and the pre-adsorbed HGG biomolecule inhibit the adsorption of BSA molecules on the a-C film surface.Both of them forms the HGG dominant adsorbed layer on a-C film surface in the mixture solution of BSA and HGG?B+G?and the mixture solution of BSA,HGG and HA?B+G+H?.The adsorption of BSA,HGG,HA influence the tribological behavior of a-C film and Al₂O₃ tribo-pair.In BSA solution,the BSA-adsorbed layer is easily peeled off from hydrophobic a-C surfaces for low cohesive strength under shear force.This increases the wear of a-C film.In HGG solution,during sliding,the HGG-adsorbed layer at the wear track protects a-C film from wear.In B+G solution,BSA diffuses about 1.3 times faster than globulin HGG.During sliding,BSA molecules is adsorbed more quickly than that HGG molecules from solution.This inhibits the repair of HGG adsorbed layer formed before wear.This results in that the wear volume in B+G is higher than that in HGG solution.In HA solution,HA molecules can decrease the friction coefficient.And when HA is present in B+G+H solution,the wear volume is lower than that in B+G solution.The changes of load and velocity will affect the tribological behavior of a-C film in HGG solution.With the increasing of loads,the increasing contact stress results in that the HGG adsorbed layer are peeled off a-C film easily and a-C films lose the protecting layer.The friction coefficient decreases and the wear volume increases.With the increasing of velocity,there is no enough time for the adsorption of HGG during rubbing,it results in the losing of HGG protecting layer and the increasing of wear.The existing of hydrogen in carbon-like film affects the adsorption of BSA and HGG,and then affect the tribological behavior of carbon-like film.BSA molecules and HGG molecules form a adsorbed layer with end-on orientation on a-C:H film.The BSA-adsorbed layer can cohesive with hydrophilic a-C:H film well under shear force.The wear volcume of a-C:H film is 5.0 E-5 mm³,which is lower that in BSA solution for a-C film?1.1E-4 mm³?.In HGG solution,the HGG molecules on hydrophilic a-C:H film can be peeled off easily.The wear volcume of a-C:H film in HGG solution is 7.1 E-5 mm³,which is higher than that for a-C film in HGG solution?8.0 E-7 mm³?.In B+G solution,BSA molecules is adsorbed more quickly on hydrophilic a-C:H film than that HGG molecules from solution,and the adsorbed BSA can be peeled off hard.This results in that the wear volume of a-C:H film in B+G solution is 3.2 E-5 mm³,which is lower than in BSA or HGG solution.Compared to a-C film,the wear volume of a-C:H film in HGG solution is biggest,and the wear volumes of a-C:H film in BSA and B+G solutions decrease.