Cheolgyu Kim1 Jongmin Kim2 YoungShin Song2 Seong-Geun Jeong2 Chang-Soo Lee2 Taek-Soo Kim1

1, KAIST, Daejeon, , Korea (the Republic of)
2, Chungnam National University, Daejeon, , Korea (the Republic of)

In this study, we demonstrated a methodology for the design and simulation of self-bending bilayer microstructures using pH-sensitive hydrogels. The goal of this study is to characterize the performance of self-bending behavior, provide fundamental information for engineering design, and validate simulations of physics-based models with experiments, theoretical approach, and finite element method (FEM) simulation. The self-bending behavior of hydrogel bilayers, composed of an active layer and a passive layer, is completely reversible and allows the structure to fold and unfold without permanent deformation. The effects of design parameters on the self-bending behavior of the microstructures of hydrogel bilayers are explored by varying the extrinsic geometric variables. The study of FEM simulations verifies that the final shape of the bilayer sheet is governed by intrinsic properties, such as the elastic modulus and the swelling ratio, and extrinsic geometrical factors, including the thickness ratio of the bilayer and the aspect ratio of the structure. Self-bending flower-shaped microstructures can be realized by a simple bilayer concept. Simultaneously, programmable deformation of self-bending microstructures can be simulated, forming a basis for the design of relevant actuating models. This simple reversible actuating system is, therefore, promising for a wide range of applications, such as delivery systems, cell encapsulation, artificial tissue, and soft robotics, owing to its simplicity of fabrication, high reversibility of actuation, and biocompatibility of materials. This fundamental investigation not only provides insights into the bending of bilayer microstructures but also has important implications for responsive and intelligent soft matter.