471940 A Quantitative Theory of Magnetic Janus Particle Assembly

Thursday, November 17, 2016: 10:00 AM
Union Square 23 & 24 (Hilton San Francisco Union Square)
Thomas Long1, Joel Koplik2 and Ilona Kretzschmar1, (1)Chemical Engineering, The City College of New York, The City University of New York, New York, NY, (2)Department of Physics, Levich Institute, City College of New York, New York, NY

Under a magnetic field, Janus particles with magnetic caps (magJP) assemble into 2D chains. These chains give the fluid they are immersed in interesting rheological properties. More specifically, the longer the chains, the greater the viscosity. The rate of the magJP assembly is dependent on the dipole strength of the particles and is studied in this project. Predicting and controlling the magJP assembly rate will enable the engineering of materials that have desirable properties.

We have carried out experiments that measure the assembly rate of the magJP chains. The particles are synthesized, confined to a 2D environment, placed in a magnetic field, and tracked as they assemble. Particle tracking software has been developed for the project, and has been used to collect information from the videos including: chain concentrations vs time, particle trajectories, and dipole-dipole interaction energy. The results are fit to the Smoluchowski coagulation equations to obtain rate constants for chain aggregation.

The talk will discuss the relevance of these rate equations. A theory is proposed for prediction of the magJP rate constants when varying: concentration, dipole strength, dipole shift, viscosity, and particle size. The theory is shown to predict the magJP rate constants and future experiments are proposed to further test the theory.


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See more of this Session: Active Colloidal Systems
See more of this Group/Topical: Engineering Sciences and Fundamentals