Crosslinker concentration effect on the poroviscoelastic relaxation of polyacrylamide hydrogels using depth-sensing indentation

Abstract

The effect of crosslinker concentration on the mechanical behaviour of polyacrylamide based hydrogels is established by using depth sensing indentation. In this work, hydrogels are considered as poroviscoelastic solids, being viscoelasticity and poroelasticity taken into account at intermediate length scales such as those here explored. A constrained fitting method is derived to implement a multiplicative rule that accommodates the contribution of each deformation mechanism on the global material response. The proposed method is robust enough to properly separate poroelastic and viscoelastic contributions from relaxation curves measured at different indentation depths and strain rates. At the length scales here tested viscoelasticity appears as dominant, but the poroelastic contribution becomes increasingly important as the crosslinker concentration is reduced.