Effect of walls on the motion of magnetically driven superparamagnetic microparticles

In microfluidics studies, it is often (implicitly) assumed that particles follow the surrounding flow. The effect of boundaries is, therefore, neglected. In the present paper, we investigate—experimentally and theoretically—the situation wherein the presence of boundaries affects the dynamics of particles. We designed and fabricated a tool to detect particle positions and measure their displacement and velocity to study the effect of wall on magnetically driven superparamagnetic microparticles (SMP). Two experimental setups are employed. A vertical setup is operated in free particle migration mode where the particle motion is not affected by the chip boundaries. We here measure the density and the magnetic susceptibility of the particle. This setup allows to characterize particle properties and to calibrate the interaction of the particles with the external magnetic field. In a horizontal setup, we track migration with the particle motion affected by the presence of channel bottom.