Fig. 6

Solvent-responsive anisotropic actuating performance. a, b Schematic illustration of actuator mechanism for the SNPP gel piece when exposed to poor solvent. In situ real-time optical monitoring the bending process of gel piece with the lamellae perpendicular (c) and parallel (d) to the top surface when placed in ethanol, from top and side views, respectively. All the scale bars in c, d are 5 mm. e Schematic illustration of assembly of robotic arm by two hydrogel pieces with lamellae in different orientations through a healing procedure. f, g Combined with the anisotropic structures, the integrated hydrogel piece exhibits distinct actuations varied from the parts when placed in ethanol, just like a robotic arm with vertical lifting. h Further optical image proves the in-plane and out-of-plane deformations. i Schematic illustration of complicated assembly of robotic hand composed of two fingers and one palm and conducted by three hydrogel pieces with lamellae in different orientations through a healing procedure. j–l The integrated hand shows a grasping action when immersed in ethanol