Light-Controlled Adhesive Hydrogels for On-Demand Adhesion.

The rapid and reversible adhesion between solids is of great significance, particularly in fields such as biomedicine, intelligent machines, and bioelectronic sensors. Hydrogels, as soft materials, play a vital role in reversible adhesion. To achieve a wider range of applications, it is essential to enhance the intelligence of hydrogels. However, the preparation of reversible adhesive hydrogels with remote control, reversible adhesion, rapid response, and no residue remains a challenge in the field. Herein, we developed a light-controlled reversible adhesive hydrogel by integrating temperature-controlled reversible adhesion with the photothermal response capabilities of FeO. The hydrogel can adhere/desorb reversibly under temperature control and allows for remote adhesion control using infrared light. Under infrared light irradiation, surface water causes carboxylic acid groups to migrate to the surface, thereby shielding the catechol groups. This results in insufficient adhesive groups at the interface to form interactions with opposing surfaces. Without infrared light irradiation, the adhesive functional groups are exposed, allowing interaction forces to form between the surface with the adhesion groups and the opposing surfaces. This smart hydrogel holds significant potential for future applications in wound dressings, wearable devices, and soft robots.