Thermally Responsive Hydroxypropyl Cellulose/Polyacrylamide Hydrogel with Programmable and Reversible Adhesion

The development of adhesives with switchable and programmable adhesion in both air and water environments is highly desirable but still difficult to realize. Here, we have developed a smart hydrogel with programmable and reversible adhesion behavior under thermal stimuli by introducing a thermally responsive hydroxypropyl cellulose (HPC) polymer unit into the hydrogel network. By alternately lowering and raising the temperature of the hydrogel, the transition from a sticky to a nonsticky state was achieved in both air and water environments, with a wide switching range between high and low adhesion, fast switching speed, and durable switching efficiency. Accurate and fine control of dry and wet adhesion strength can also be achieved by changing the temperature of the hydrogel. In addition to adhesion performance, the surface wettability, mechanical properties, and optical transmission of the hydrogel also adapt to temperature stimuli and can be programmed and switched in response to temperature change. By exploiting its programmable and switchable adhesion capacity, the hydrogel is demonstrated as a smart gripper for the controllable capture and release of objects in air and underwater environments. This study opens a path for the design of programmable adhesives, responsive materials, and smart devices.