Thermally controlled large deformation in temperature-sensitive hydrogels bilayers

The present work investigates the thermally controlled deformation characteristics in temperature-sensitive hydrogels bilayers. The free energy density for temperature-sensitive hydrogels is modified, upon which the finite element model is developed and implemented through user-defined material subroutine UHYPER in the commercial software ABAQUS. The modified UHYPER implementation allows for more vividly depicting the continuous deformation in phase temperature region for temperature-sensitive hydrogels. Several thermally controlled cases of temperature-sensitive hydrogel including grippers, self-folding boxes, thermally driven origami are presented to illustrate a wide array of complex interesting applications or phenomena. Furthermore, we develop a simple model to theoretically calculate the bending angle of the temperature-sensitive hydrogel bilayers, which has been validated by the finite element simulation results. Our study can provide more insights for optimal design in thermally controlled hydrogels structures.