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Published on: August 2, 2012
Viscosity control of the dynamic self-assembly in ferromagnetic suspensions
D L Piet1, A V Straube, A Snezhko
1Department of Engineering Science and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Physical Review Letters
|May 28, 2013
Summary
Liquid viscosity controls dynamic self-assembly in magnetic colloids. Lower viscosity favors snake structures, while higher viscosity promotes asters, offering a method to direct colloidal self-organization.
Area of Science:
- Physics, Soft Matter
- Materials Science, Nanotechnology
Background:
- Ferromagnetic colloids exhibit dynamic self-assembly at liquid interfaces.
- Structures range from linear snakes to axisymmetric asters, with associated hydrodynamic flows.
Purpose of the Study:
- Investigate the governing factors of structure transitions in dynamic self-assembly.
- Determine the role of suspending liquid viscosity in self-assembly outcomes.
Main Methods:
- Controlled experiments with ferromagnetic colloids.
- First principles theoretical analysis.
- Analytic solutions of time-averaged Navier-Stokes equations.
Main Results:
- Liquid viscosity dictates the transition between snake and aster structures.
- Less viscous liquids yield snakes; more viscous liquids yield asters.
- Hydrodynamic flows and force balance are crucial for self-assembly.
Conclusions:
- Viscosity is a key parameter for controlling dynamic self-assembly in magnetic colloidal suspensions.
- Understanding viscosity-driven transitions enables predictable structure formation.
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