Magnetically Actuated Jamming

For robotic systems to have versatile interactions with their environment, their structural components need mechanical tunability, enabling them to match the mechanical impedance (stiffness and damping) of their environment. For example, they need to be stiff when precision is required, yet soft when conformability and adaptability is required. Jamming is a mechanical phenomenon in which a cluster of constituents exhibit dramatic changes in its bulk mechanical behavior when the coupling between the individual constituents is altered. Existing jamming actuation methods, such as pressure or voltage are not particularly compatible for robotic tasks in hard-to-reach and high-risk areas such as constricted areas inside the human body, because they require the structure to be tethered via tubing or wiring or require bulky on-board actuation mechanisms. Magnetic fields offer a solution to this problem by enabling remote actuation. Here, we will talk about how ferromagnetic composite materials can achieve programmable jamming behavior when an external magnetic field is applied. We outline design guidelines for magnetic jamming structures, and enable effective jamming behavior in multiple dimensions despite external magnetic fields along single directions. We model and describe the mechanical behaviors which are linked to the magnetic forces and torques. Our work demonstrates a novel jamming actuation modality which can have tunable directional control of mechanical properties such as stiffness, yield, and plasticity.