Behavior of an FG temperature-responsive hydrogel bilayer: Analytical and numerical approaches

Abstract

Sensitive hydrogel bilayers have recently been used for many purposes, such as sensors and actuators etc. In this paper, an innovative analytical technique is introduced to study the finite bending of a bilayer, including a thermally-activated functionally graded hydrogel layer which is connected to a neutral incompressible elastomeric one. In the hydrogel layer, the amount of cross-linking density changes linearly or exponentially in the thickness direction. The governing equations of the bilayer are developed and solved considering the additive decomposition of the free energy for the hydrogel and incompressibility of the elastomer using appropriate boundary conditions. To check the validity of the analytical technique, the deformation of the bilayer occurred by the virtue of temperature variations is modelled using the finite element method (FEM), and the results are extracted and compared with the analytical approach. The results of both approaches were in perfect agreement, demonstrating that the presented method is reliable and robust. In addition, the effects of some geometrical and material characteristics on the bending behavior of the bilayer were examined, and it was discussed whether there are any optimum values for these parameters for the bilayer under various conditions.