Articulated Untethered Magnetic Actuators for Multimodal and Cross-Scale Operations.

Untethered magnetic actuators hold great promise for minimally invasive medicine, yet reconciling functional versatility with simple, reliable control remains a critical challenge. To address this, we introduce a modular design paradigm that employs revolute joints to interconnect discrete rigid modules. This strategy synergizes the mechanical robustness of rigid systems with the reconfigurability of soft robots, imparting additional degrees of freedom that enable complex, on-demand deformations. We demonstrate this approach through articulated prototypes capable of executing diverse locomotion strategies, including crawling and rolling, while leveraging on-demand mode switching to perform functional tasks such as cargo transportation, stirring and release. A critical advantage is that all locomotion and mode transitions are driven by a single, uniform magnetic field, thereby decoupling control from function and simplifying the system architecture. The robustness of the mechanism is confirmed through mathematical simulations and a dimensionless analysis that validates its feasibility across scales. The platform's versatility is ultimately demonstrated by its high-dexterity navigation through a tortuous vascular phantom and its successful execution of targeted cargo delivery within an ex vivo porcine stomach model. This work establishes a readily controllable and scalable framework for designing multifunctional magnetic robots, paving the way for high-precision operations within complex biological environments.