Electrical Writing to Three-Dimensional Pattern Dynamic Polysaccharide Hydrogel for Programmable Shape Deformation.

The ability to pattern and actuate hydrogels is essential for biomimetics, soft robotics, and biosensors. Here an electrical writing technique with the capability to create both surface and across thickness patterns in dynamic chitosan-H+ /agarose hydrogel by electronically generated pH gradient is introduced. The diffusible pH cues deprotonate and re-assemble chitosan chains by hydrogen bonds, changing the electrical writing domains from original loose structure to a dense layer and resulting in different mechanical stress and swell ability that causes the hydrogel to deform. The deformable trend can be modulated by writing depth and selective writing area on the surface, and significantly enhanced by temperature increment. Finally, a dual electrical writing process to create three-dimensional patterns and demonstrate programmable shape transition by differing patterns is performed.