Assembly of colloidal building blocks into complicated structures is of fundamental and    technological importance for their applications in photonics and devices. External fields are also frequently used for directing colloids not only for studying the equilibrium behavior but also for drug delivery and cancer therapy. Here we employ precisely controlled, to a micrometer scale, external magnetic fields to direct assembly of binary colloidal systems into colloidal crystals or into interesting core-shell assemblies. It is known that non-magnetic particles dispersed in a ferrofluid can be directed by magnetic field gradients since the pioneering work of Skjeltrop (Phys. Rev. Lett. 51  , 2306, 1983  ). Recently this principle was employed to assemble multipolar colloids and 2D crystals of colloids. We use magnetophoretic forces (magnetic forces in a field gradient) to specifically direct magnetic and non-magnetic particles into specific spots, which may find applications in photonics and devices due to functionality brought by the binary nature of the system.

Binary colloidal crystals: Directed-assembly using external magnetic fields

243rd National Meeting (2012)

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