Clickable Microgel Inks Enable Spatioselective, Multi-Stimuli Programmable Assembly of Materials.

Life-like materials that can dynamically morph their shape/texture, inspired by living organisms such as cephalopods are sought after for soft robotics and camouflage applications. Achieving such functions demands multimaterials with spatially programmed responses, yet their creation remains challenging. The existing approaches have been limited by the specific in situ polymerization conditions, fluidity of the synthetic components, and the complex, multi-step processing requirements. Here, we propose a universal strategy that enables programming of material response within pre-synthesized, ready-to-use, clickable microgels with different response behaviors. These microgels can be deposited within desired regions of the material structure via direct ink writing to enable pre-programmed, localized responses to external stimuli. Spontaneous interparticle stabilization of the deposited microgels via a click reaction (Diels-Alder bonding) yields shape-stable, free-form granular hydrogel multimaterials with reversible, repeatable, and spatially selective responses to stimuli (e.g., pH and temperature). The strategy establishes a 4D-printing-compatible, scalable modular platform for facile fabrication of soft materials with programmable shape adaptivity.