Exploring an alternative aqueous lubrication concept for biomedical applications: Hydration lubrication based on O/W emulsions combined with graphene oxide

Water-based lubrication concepts are of high interest for applications that require friction and wear control in a bio-medical environment. In this work, a concept of aqueous lubrication is presented based on hydration of surface active polymers combined with graphene oxide. Three different kinds of surface-active polymers with or without graphene oxide were coated on a CoCrMo alloy surface, and the samples were characterized by ATR and XPS. Hydration lubrication was created from a tailored oil-in-water (O/W) emulsion. Enhanced friction reducing capability was found for the polymeric coatings in combination with graphene oxide. The tribological behaviour of a PEG-lactide coating in emulsion was better than that of PEG coating, indicating the advantage of using hydrophilic and lipophilic group containing surface-active polymers for emulsion lubrication. The overall maximum reduction in friction that was achieved for a sliding contact of coated engineering surfaces from CoCrMo at low sliding velocity and moderate contact pressure was of about 63% compared to uncoated CoCrMo sliding in water at the same operational conditions.