4D Printing of Hydrogels Controlled by Hinge Structure and Spatially Gradient Swelling for Soft Robots

In 4D printing, structures with gradients in physical properties are 3D printed order to dramatically increase deformation. For example, printing bilayer passive and active layers has been proposed, however, these methods have the disadvantages that material of each layer is mixed, modeling process complicated. Herein, we present a method creating gradient gels different degrees polymerization on UV-exposed side other using single by simply increasing amount initiator. This gel first example which differential swelling ratio between two sides causes curl inward toward side. The mechanical (swelling Young’s modulus) were measured at concentrations structures, effects deformation analyzed simulated. results show adding an initiator concentration 0.2 (mol/L) or more deformation, crosslinker factor three increases hinge structure limits up 90°. Thus, it was found maximum can be predicted some extent simulation. future, will able create complex while utilizing