title: Viscoelasticity of dynamically self-assembled paramagnetic colloidal clusters.
abstract: Paramagnetic particles in a liquid above a solid dynamically self-assemble into two-dimensional (2D) viscoelastic clusters in a processing magnetic field if the precession angle exceeds the magic angle. Hexagonal clusters rotate with a frequency proportional to the precession frequency of the magnetic field. The rotation is explained by viscoelastic shear waves excited in the clusters that can be visualized slightly above the magic angle. The cluster rotation and the visualization of viscoelastic modes are independent techniques to probe the rheological properties of the cluster. We find agreement between both techniques when determining the 2D cluster viscosity eta(c) approximately 10(-11) N s/m.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA.
authors.forename: Pietro
authors.initials: P
authors.lastname: Tierno
authors.forename: Ramanathan
authors.initials: R
authors.lastname: Muruganathan
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Fischer
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004548:Elasticity; D008280:Magnetics; D008956:Models, Chemical; D011137:Polystyrenes / Q000737:chemistry; D014783:Viscosity
chemical_list: D003102:Colloids; D011137:Polystyrenes