Direct ink writing of soft polymer matrices enables on-the-fly shape morphing in soft robots

Abstract

Soft robots, with their inherent compliance in material and structure, offer new opportunities for adaptable locomotion in unstructured and confined environments. The ability to reconfigure body shape for switching between locomotion modes and gaits is becoming a defining feature of soft robotic mobility, yet achieving such reconfiguration through non-contact, monolithic actuation remains a challenge. Here, we introduce a magnetically actuated soft robot capable of on-the-fly shape morphing, enabled by direct ink writing of soft polymer matrixes. The robot is monolithically fabricated by depositing shape memory polymers (SMPs) with embedded functional particles—NdFeB for actuation and Fe₃O₄ for localised heat concentration—into a multi-material architecture that enables on-the-fly shape morphing under dual magnetic fields. This method expands the design freedom of the robot architecture through direct ink writing of soft and functional polymers and enables actuation and shape transition using only magnetic fields. High-frequency magnetic fields adjusted the stiffness of the robot body by localised heat concentration, while low-frequency fields induce shape change and locomotion. Once reconfigured, the robot locks into a new shape and continues movement in a new mode, such as crawling, rolling, or jumping. We demonstrate robust locomotion, environmental adaptation, and targeted load-bearing delivery across multiple terrains.