Tribological properties of microporous polydimethylsiloxane (PDMS) surfaces under physiological conditions

Textured biomaterials have been extensively used in biomedical engineering to modulate mammalian and bacterial cell adhesion and proliferation, implant integration with human body and infection prevention. However, the tribological implications of texturing under wet physiological conditions have not been well quantified. This study aimed to characterize the tribological properties of micropore-textured polydimethylsiloxane (PDMS) under physiological conditions and investigate the effect of adsorbed lubricious molecules on friction. In this study, untextured and micropore-textured PDMS surfaces were slid against curved smooth glass surfaces under the contact pressures of 10-400 kPa, sliding speeds of 0.1-5 mm/s in aqueous solutions with the viscosity of 1-1000 mPa·s. Reconstituted human whole saliva (RHWS) at pH 7 and porcine gastric mucin (PGM) at both pH 2 and 7 were used as lubricious coatings on PDMS. While the micropore-texturing delayed the transition of lubrication regimes, it increased the coefficient of friction (COF). Although RHWS and PGM coatings decreased the COF significantly, the protein coatings could not help the COF of micropore-textured surfaces getting lower than that of untextured surfaces. The results suggest textured polymeric surfaces could generate larger friction under physiological conditions and lead to a higher chance of inflammation near the implants.