title: Binary colloidal structures assembled through Ising interactions.
abstract: New methods for inducing microscopic particles to assemble into useful macroscopic structures could open pathways for fabricating complex materials that cannot be produced by lithographic methods. Here we demonstrate a colloidal assembly technique that uses two parameters to tune the assembly of over 20 different pre-programmed structures, including kagome, honeycomb and square lattices, as well as various chain and ring configurations. We programme the assembled structures by controlling the relative concentrations and interaction strengths between spherical magnetic and non-magnetic beads, which behave as paramagnetic or diamagnetic dipoles when immersed in a ferrofluid. A comparison of our experimental observations with potential energy calculations suggests that the lowest energy configuration within binary mixtures is determined entirely by the relative dipole strengths and their relative concentrations.
authors.affiliation: Duke University, Department of Mechanical Engineering and Materials Science, Center for Biologically Inspired Materials and Material Systems, PO Box 90300 Hudson Hall, Durham, North Carolina 27708, USA.
authors.forename: Karim S
authors.initials: KS
authors.lastname: Khalil
authors.forename: Amanda
authors.initials: A
authors.lastname: Sagastegui
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.forename: Mukarram A
authors.initials: MA
authors.lastname: Tahir
authors.forename: Joshua E S
authors.initials: JE
authors.lastname: Socolar
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Wiley
authors.forename: Benjamin B
authors.initials: BB
authors.lastname: Yellen