Out-Of-Equilibrium Hydrogel Microrobots Exhibiting Autonomous Deformation, Controllable Autolysis, and Directed Locomotion

Access to multifunction-integrated hydrogel microrobots is highly desired in many complex application scenarios, yet remains a challenging task. Here, adaptive out-of-equilibrium hydrogel microrobots exhibiting autonomous deformation, controllable autolysis, and directed locomotion in response to orchestrated chemical and physical signals are reported. These hydrogel microrobots are prepared by crosslinking carboxyl-decorated polymers through coumarin dimerization. Upon the addition of carbodiimide as a chemical fuel, the hydrophilic carboxyl groups are converted to hydrophobic anhydrides, leading to shrinking of the microrobots. However, with the depletion of fuel, the formed anhydrides spontaneously hydrolyze to the initial carboxyl groups, thus resulting in an autonomous swelling of the microrobots to their original size. Moreover, because of the efficient photocleavage of coumarin dimers, the microrobots can rapidly disintegrate (<10 min) upon irradiation. With the incorporation of magnetic powders, these hydrogel microrobots can be guided to move in space by a magnetic field. By virtue of these seamlessly integrated functions, the hydrogel microrobots can be manipulated to adaptively move through a narrow terrain and release the loaded cargo at a target position. This work may boost the development of multifunction-integrated lifelike soft robots for many complicated applications ranging from precision drug delivery to non-invasive therapies.