Transient swelling-induced finite bending of hydrogel-based bilayers: analytical and FEM approaches

Hydrogels with their time-dependent intrinsic behaviors have recently been used widely in soft structures as sensors/actuators. One of the most interesting structures is the bilayer made up of hydrogels which may undergo swelling-induced bending. In this work, by proposing a semi-analytical method, the transient bending of hydrogel-based bilayers is investigated. Utilizing nonlinear solid mechanics, a robust semi-analytical solution is developed which captures the transient finite bending of hydrogel-based bilayers. Moreover, the multiphysics model of the hydrogels is implemented in the finite element method (FEM) framework to verify the developed semi-analytical procedure results. The effects of different material properties are investigated to illustrate the nonlinear behavior of these structures. The von-Mises stress contour extracted from FEM shows that the critical area of these soft structures is at the interface of the layers which experiences the maximum stress, and this area is most likely to rupture in large deformations.