Programmable 3D Morphing Bionic Gradient Hydrogel Actuators with Fast Response and Large‐Amplitude Deformations

Hydrogel actuators have shown promising applications in biomedical devices, wearable electronics, and soft robotics. To fulfill practical applications, hydrogel actuators must achieve high-speed adaptive motion, programmable large-strain actuation and 3D morphing ability, however, the fabrication of such actuators remains a challenge. In this work, temperature responsive gradient hydrogel is prepared through the UV-absorbing effects of the precursors at specific wavelength of UV light during photopolymerization. Moreover, chito-oligosaccharides (COS) are introduced to enhance the hydrogel's gradient structure by migrating to the low-density side during photopolymerization and acting as porogen, resulting in a hydrogel with an ultrafast bending rate (190°/s) and large amplitude (760°). Furthermore, a light-responsive gradient hydrogel can be easily fabricated using the "naturally derived" genipin-crosslinked gelatin network as the photothermal transducer. By employing the photomask techniques to customize the local gradient structures, hydrogels with programmable 3D₁-to-3D₂ deformation behavior are realized. Inspired by inchworms and springtails, the hydrogels are pre-programmed to harness its fast-response and large-amplitude deformation, enabling light-driven soft robots to achieve biomimetic actuation, including tumbling, jumping, and crawling. This programmable, fast-response, 3D shape-morphing gradient hydrogel actuator expands the possibilities for applications in complex dynamic systems, including soft robotics and bionic devices.