(548b) PSRI Fluidization and Fluid-Particle Systems Award: Dynamics of fluid-particle systems of magnetically responsive Janus particles

This talk will highlight two recent areas of our research on magnetically-responsive Janus particle systems. Fabricated through continuous roll-to-roll deposition and subsequent physical vapor deposition, these silica or polymeric micro- spheres are half coated in iron oxide. At the colloidal scale, suspensions of magneto-responsive Janus colloids form chains and undergo alignment under the influence of a magnetic field. When the magnetic field is aligned with a light path, light transmission through the sample increases as compared to randomly or orthogonally oriented chains. This study investigates the emissivity response of this suspension using visible and infrared light as a function of particle concentration and magnetic field strength. At the granular scale, a magnetic force can be used to tune both the torque and interparticle attraction to tune the motion and friction of dense granular systems. These responsive microroller robotic Janus particles flow with quintessential granular behavior, such as surface layer flow, but against gravity, giving rise to a negative angle of repose and a negative coefficient of friction. These systems also readily segregate and demonstrate creep as granular materials, suggesting granular physics can be used to optimize how to manipulate microroller systems over obstacles and through complex geometries. Rather than studying how robots can navigate granular media, the granular media itself is the responsive material that is manipulated as an amorphous particle- based soft-robot.