Non-linear rheological study of hydrogel sliding friction in water and concentrated hyaluronan solution

Studying sliding friction of hydrogels in liquid is important for understanding biological friction. This work applies the non-linear rheology approach to study the friction of elastic hydrogels against adhesive glass in water and in concentrated hyaluronan (HA) solution. Using a rheometer in parallel plate geometry, stress-strain Lissajous curves are obtained from the oscillatory strain sweep test. Non-linearity and energy dissipation are characterized the strain-hardening ratio S, and "energy dissipation occupancy"., respectively. For friction in water, a clear transition from a linear viscoelastic to non-linear viscoelastic response occurs at a critical strain amplitude. Whereas, in HA solution, significant friction reduction and non-linear viscoelastic response occurs, related to the rheological behaviors of HA film intercalated at the gel/glass interface.