(683b) Dynamics of Colloidal Droplets in Rotating Magnetic Fields

Applying external magnetic fields to paramagnetic particles allows for tunable interaction potentials as they contain induced dipole moments. In this work, we use rotational magnetic fields to generate interactions that are strong enough to allow the particles to assemble into ordered structures, yet weak enough to allow for them to rearrange into a configuration that leads to minimization of free energy. This drives the formation of circular two-dimensional colloidal clusters, which rotate similar to hard disks, yet grow and coalesce similar to that of liquid droplets. We explore the dynamics of the system such as the rate of growth and coalescence of the colloidal droplets as they try to reach equilibrium. These dispersions of “colloidal droplets” are characterized by calculating their interfacial tension using surface excess energy. The bond orientation order parameter was also measured as a function of distance away from the center of mass. This system provides insight into the dynamics of droplet migration and coalescence on the molecular level.