Magnetohydrodynamic-Driven Design of Microscopic Endocapsules in MRI

Microscopic medical robots capable of translating in a bloodstream or similar liquid represent a new type of therapeutic technology for surgical interventions. This study aims to characterize a new MRI compliant method of propulsion for swimming robots using the magnetohydrodynamic effect (MHD). An MHD drive is a method of propulsion employing only electromagnetic elements, without the need for moving mechanical parts. By utilizing MHD voltages induced within the MRI magnetic field, the opportunity to propel a device and provide imaging simultaneously is presented. We hypothesized that a wireless MHD-driven thruster could be developed to control endocapsules within the MRI magnetic field. A model capsule was constructed and evaluated in a scaled MRI-environment, and subsequently, tested for MRI-compatibility at 3 T. Dynamic performance of the endocapsule was characterized as input power was varied. In the scaled MRI environment, a peak force of 0.31 mN was observed, providing evidence that an MHD-driven endocapsule is possible in an MRI environment. Increased forces will be obtainable with increases in magnetic field strength and applied power.