(255i) Deformation Dynamics of Paramagnetic Colloidal Clusters in Time-Varying Fields

Micron-sized superparamagnetic colloids placed in time-varying magnetic fields can provide rich dynamics depending on the magnetic field applied and the particle concentration. In symmetric magnetic fields, a long-range attractive potential is induced resulting in the formation of colloidal clusters, which assemble into clusters that exhibit fluid-like behavior at relatively low fields, while becoming crystallized and highly ordered at higher field strengths.

Apart from undeniable use in photonics and semiconductor industries, these clusters can serve as probes in rheological studies due to their tunable viscoelastic properties. However, very little is known about the rheological behavior of these clusters. Here, we are studying the deformation dynamics of these colloidal clusters using a time-varying magnetic field. The deformed clusters relax to a lower energy state via bulk or interfacial rearrangement. We show relaxation time as a function of field strength and cluster size, which is associated with rheological properties such as elasticity, line tension, and viscosity.