An efficient magnetic approach for manipulating dispersed non-magnetic particles on surfaces and microchannels

Recently, there has been significant interest in understanding the behavior of magnetic particles in aqueous media under external excitations. The dynamics and self-organization of these systems, especially in the presence of time-dependent excitations, have been extensively studied due to their relevance in both fundamental physics and technological applications. In this study, we employ three Helmholtz coils to generate elliptically polarized fields. This configuration is utilized to manipulate micrometer-sized nickel and iron particles located at the bottom of a container filled with an aqueous medium. By analyzing video-microscopy images, we investigate the time-dependent displacement of these particles. Notably, we observe the formation of chain structures known as ?rollers?, whose movement on the vessel?s bottom plane can be controlled through the applied magnetic field. Furthermore, we demonstrate that the introduction of glass microspheres results in induced motion due to the displacement and drag exerted by the magnetic structures. Exploiting this effect, we successfully control the movement of glass beads along microchannels. Our findings suggest potential applications for targeted cargo delivery using this simple approach.