Tailorable non-linear viscoelastic behavior of hydrogels

In this work, we investigate the viscoelastic properties of hydrogels through stress relaxation experiments to better understand the force-dependent dynamics of these materials with the aspiration of expanding their application envelope within the biomedical field and beyond. We experimentally studied the viscoelastic behavior of 4 different types of hydrogels: covalently crosslinked polyacrylamide (PAAm), covalently crosslinked PAAm network immersed in a viscous alginate solution, ionically crosslinked alginate along with crosslinked PAAm-alginate double network. Through our investigations, we demonstrate that we can tailor the viscoelasticity of a covalently bonded PAAm network by tuning the viscosity of the solution in the gel. Moreover, based on the stress relaxation test of ionically crosslinked alginate gel and the double network gel, we have revealed the quantitative correlation between the ionic bond dissociation and force-dependent viscoelastic behavior of gels containing ionic crosslinks.