Tough Interfacial Adhesion of Bilayer Hydrogels with Integrated Shape Memory and Elastic Properties for Controlled Shape Deformation.

The weak adhesion between two hydrogel layers may lead to the delamination of bilayer hydrogels or low force transfer efficiency during deformation. Here, tough interfacial adhesive bilayer hydrogels with rapid shape deformation and recovery were prepared by simple attachment-heating of two gel layers. The bilayer hydrogels, composed of a shape memory gel (S-gel) and an elastic gel (E-gel), exhibited extremely tough interfacial adhesion between two layers (Γ ∼ 2200 J/m2). The shape deformation and shape recovery of the bilayer hydrogels, tuned by "heating-stretching" mode and "stretching-heating-stretching" mode, were rapid (<5 s) and no delamination between two gel layers was detected during shape deformation. Based on the fast shape deformation and recovery, the bilayer hydrogels could mimic the flower and hand, and a gel gripper could be fabricated to catch the object in the hot water. This work provides a simple method to prepare tough adhesive bilayer hydrogels with controlled shape deformation.