Assembly of microscopic particles into macroscopic structures can open new pathways for the fabrication of complex materials and devices that cannot be produced via lithographic methods. Here we demonstrate a versatile colloidal assembly system in which the design rules can be tuned to yield over 20 different pre-programmed structures, including kagome, honeycomb, square tiles, as well as various chain and ring configurations. These structures can be dynamically tuned with the external field. The assemblies are created by controlling the relative concentrations and interaction strengths between spherical magnetic and non-magnetic beads, which behave as either paramagnetic or diamagnetic dipoles when immersed in a ferrofluid. An external magnetic field causes like particles to repel and unlike particles to attract. The combination of experimental observations and potential energy calculations suggest that the lowest energy configuration is determined by two parameters, namely the relative strengths of the two dipole moments and their relative concentrations.

Magnetically directed assembly and dynamic manipulation of binary colloidal crystals

245th National Meeting (2013)

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