Swelling-induced Morphological Deformation and Constitutive Relation of Soft Materials in Micro-patterned Hydrogel

Soft materials are ideal for designing structures with useful properties. Especially, hydrogels have been extensively studied for their response to various external stimuli and reversibility. A gel under geometric confinements deforms anisotropically due to applied directional stresses, but otherwise it can be equilibrated and swollen by solvent homogeneously. In particular, wrinkling instability can be observed for line patterns of hydrogels bounded on a rigid substrate. Geometry and swelling ratio of the gel can decide a morphology – in the case of wrinkles, wavelength and amplitude - of the pattern. We controlled not only geometry factors of the micro patterns of hydrogl , but also the swelling ratio of the gel by varying the amount of Acrylamide (AAm) added during synthesis.
There has been much research on the effect of geometry on mechanical instability. However, in-depth studies on the material properties and constitutive law related to the swelling ratio of the gel have not been conducted. In this presentation, we propose modified nonlinear stress-strain relationship of our synthesized gels in scope of both continuum and molecular scales and compare it with our experimental results.