Programmable and Reversible 3D-/4D-Shape-Morphing Hydrogels with Precisely Defined Ion Coordination
Zuxiang Xu, Jun Fu
Abstract
Precise and programmable control of reversible deformations of hydrogels has important implications for bionics. This work reports on programmable three-dimensional (3D) deformations and thermoresponsive actuation of polymer hydrogels in a well-defined manner. Precise infiltration of Fe3+ with periodic patterns is additionally used to cross-link the local polymer network through ionoprinting with a patterned electrode array. The patterned Fe3+ cross-linking generates periodic undulations in cross-link density, stiffness, and thermoresponsiveness. The internal stress induces 3D helical structures with tunable chirality and dimensions. The differential thermoresponsiveness imbues a fourth dimension to the shape deformations. Moreover, sequential ionoprinting generates well-defined in-plane periodic distributions of differential modulus and responsiveness, leading to 3D/4D umbrella-like origami upon temperature triggers.