(383j) Self-Guided Navigation of Magnetic Micro-Robots on Topographic Landscapes

We show how spatially uniform, time-periodic fields can direct the migration of magnetic particles up local gradients in the topography of a solid substrate. Our experiments are based on ferromagnetic Janus spheres dispersed in water above an inclined surface. Without knowledge of the particle locations or the incline direction, application of a designed field causes the particles to migrate up the incline against the force of gravity. We quantify the speed and direction of particle migration as a function of incline angle and driving frequency for different designed waveforms. Importantly, this type of “topotaxis” enables the self-guided navigation of multiple particles in a common field as directed by gradients in their respective environments. We discuss how time-varying magnetic fields can be designed and deployed to direct the self-guided navigation of micro-robots through structured environments that are otherwise inaccessible─for example, through biological tissues, battery materials, groundwater aquifers, etc.