Abstract

Soft robots operate safely in delicate, confined environments and require materials that combine softness and large deformation in complex architectures. Digital light processing (DLP) 3D printing enables such structures, but rapid curing fixes networks with short strands, limiting extensibility of printed hydrogels. Here we report a controlled post-print decrosslinking strategy that decouples shape fixation from network maturation to yield highly stretchable, strong DLP-printed hydrogels. In this design, photo-triggered, base-cleavable coupling between o-nitrobenzyl acetal and (meth) acrylate groups establishes a dense network for printing and shape fixation. Subsequent alkaline cleavage restores chain mobility and lengthens network strands, while hydrophobic side-group modification induces phase-separated domains that enhance strength. The resulting hydrogels reach 1100% strain at break and 3.7MPa tensile strength, combining high stretchability with high strength. This performance enables pneumatic actuators with 8-fold volumetric expansion and payload transport in confined fluidic environments. Our strategy provides a soft material platform for 3D-printed soft robotic systems requiring large, reversible deformation.

Fig. 1 Decrosslinking and hydrophobic reinforcement enable digital light processing (DLP)-printed hydrogels for soft actuation and robotics. A Illustration of a desired workflow for soft robots: high-precision DLP printing of complex actuator architectures followed by direct assembly. B Conventional DLP printing produces either densely crosslinked, short-chain networks with limited mobility or loosely connected networks with insufficient structural stability. C Schematic of our strategy and the associated chemical transformations. DLP printing first establishes a shape-preserving network, in which acNB-derived photochemistry introduces base-cleavable ester junctions. Subsequent acid catalyzed hydrophobic modification with dodecyl aldehyde generates hydrophobic side chains that assemble into phase-separated reinforcing domains. Finally, alkaline treatment cleaves the ester junctions, yielding a reconfigured network with increased chain mobility and effective strand length while retaining hydrophobic microphase reinforcement. D The printed hydrogels exhibit large reversible deformation, including hollow-cell inflation up to eightfold volume expansion and programmable actuation of soft robotic structures in aqueous environments.

Fig. 5 Design concept, module performance, and multimodal locomotion demonstration of the r-PVANB gel in integrated soft robotic systems. A Schematic illustration of the tardigrade-inspired quadrupedal amphibious walker, featuring a central main body and four independently controlled pneumatic legs. B Finite element simulation of displacement and corresponding photographs of a single monolithic leg actuator transitioning from the initial to the pneumatically actuated state. C Sequential optical photographs demonstrating the stepwise inflation and directional movement of the leg actuator at different time points. D Sequential photographs of the assembled robotic walker demonstrating amphibious walking capability on a water-covered inclined surface under cyclic pneumatic actuation. E Schematic illustration of the worm-like robot, showing the multi-chamber body with one elongating module and two expanding modules, and the programmed actuation sequence from T0 to T5: posterior anchoring, body elongation, anterior anchoring, and forward pulling during deflation. F Stepwise actuation process and corresponding simulation-assisted photographs of the worm-like robot during one complete expansion-anchoring-release locomotion cycle. G Sequential photographs demonstrating the peristaltic crawler transporting a payload toward a target object over four programmed actuation steps in a confined environment.

https://doi.org/10.1038/s41467-026-78658-8