Field-induced Percolation and Anomalous Diffusion in Systems of Dipolar Colloids

Sabine Klapp, Technische Universitat Berlin

Colloidal suspensions involving dipolar interactions are prime examples of soft matter systems displaying self-assembly and percolation. Moreover, these structures can be manipulated by external fields. In the present talk we discuss recent computer simulation results for two examples of such systems, focusing on the interplay of self-assembly, percolation and the (translational) dynamics of the particles. In the first part we consider ferromagnetic, spherical or rod-like, particles in static magnetic fields, which display aggregation into chains. Using Molecular Dynamics and Brownian Dynamics we demonstrate that the anisotropic, yet normal diusive behavior seen in weakly coupled systems and nite elds becomes anomalous both parallel and perpendicular to the eld at sufficiently high dipolar coupling and eld strength. The second part deals with gold-patched dielectric particles, in which an external (electric) field can induce multipolar interactions. Consistent with experiments, we find our model system to self-assemble via a two-step scenario involving first percolation along the field, followed by a percolation transition in the transverse direction. The resulting two-dimensional networks are again characterized by strongly hindered translational dynamics. Finally, we present some preliminary results for self-propelled dipolar particles. Location: CIEMAS 3399.

Date: Tuesday, Sep 24, 2013
Time: 3:00 pm - 4:00 pm
Where: See description
Contact: Grosshans, Joanne