Controllable Contact-Destructive Hydrogel Actuators.

Constructing hydrogels with spatially heterogeneous structures are crucial for unlocking novel applications. To this end, selectively removing a specific portion of hydrogels by facile and intricate destructive strategies is worth exploring. Herein, a "contact-destructive" hydrogel actuator is presented, composed of a dynamic hydrogel network doped with hydrophilic polyethylene glycol (PEG). The destructive behavior of the hydrogel actuator is attributed to the surface tension-induced spreading effect and the enhanced water absorption due to the additive PEG. Parameters that act on these mechanisms are used to control the destruction of the hydrogel. During the destructive process, the hydrogel actuator exhibits locomotion routes predetermined by the graphic pattern with the aid of 3D printing. Additionally, such self-destructive behavior can be terminated by UV light irradiation when PEG is replaced with poly(ethylene glycol) diacrylate (PEGDA). Significantly, diverse applications including controllable 3D structures collapse, self-erasing, and on-demand cell release, are realized with such self-destructive hydrogel. These results demonstrate that the present hydrogel has great values in soft robotics, anti-counterfeiting, controlled drug delivery, and other related fields.