A Novel Milli-Scale Magnetic Robot Exploiting Rotation for Controlled Magnetic Particles Release

Delivering magnetic particles to specific sites in the body offers a minimally invasive approach to drug administration, enabling precise therapeutic control and reducing systemic exposure. Yet, magnetic particle deployment typically relies on invasive tools like catheters and endoscopes, which are often unsuitable for accessing complex or confined anatomical regions. This study presents a magnetically actuated milli-scale carrier capable of navigating confined environments and performing on-demand tunable release of magnetic particles across multiple release events. Particle release is achieved through a fluidic exchange mechanism triggered by the rotation of the carrier in a fluid medium. This mechanism offers the advantage of controlling the amount of particles released by adjusting the carrier rotational frequency and duration, and it proves to be efficient, releasing over 70% of the stored particles. To ensure secure transport and minimize off-target leakage, the carrier is also equipped with a flexible magnetic cap, which limits unintended leakage to below 6%. The carrier exhibits multiple locomotion modes, including drag-based locomotion, rolling, and floating, enabled by remote magnetic control. The proposed device paves the way to less invasive and more precise targeted delivery in hard-to-reach areas of the body.