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Issue 34, 2017
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Dielectrophoretic assembly of dimpled colloids into open packing structures

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Abstract

Reversible solid-state phase transitions between open- and close-packed structures in two-dimensional colloidal crystals comprising 1.8 μm dimpled spherical colloids were observed using negative dielectrophoresis. These asymmetrically-shaped colloids adopted lattices with cmm plane group symmetry and a packing fraction, ϕ, of 0.68 at low electric field strengths. At high electric field strengths, the close-packed p6m symmetry was observed, with ϕ = 0.90. The transition between open and close-packed structures was found to be reversible, depending on the applied electric field strength and frequency. Finite Fourier transform analysis and COMSOL simulations revealed the existence of repulsive interactions between colloids perpendicular to the electric field lines due to a concentration of the electric field at the edges of the dimpled regions of the colloids. The repulsive interactions resulted in a stretching of the hexagonal lattice perpendicular to the electric field lines, the magnitude of which depended on the electric field strength. By screening the colloids from the electric field in local potential wells, the entropically favored close-packed hexagonal lattice with ϕ = 0.91 was recovered.

Graphical abstract: Dielectrophoretic assembly of dimpled colloids into open packing structures

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Publication details

The article was received on 02 May 2017, accepted on 23 Jul 2017 and first published on 25 Jul 2017


Article type: Paper
DOI: 10.1039/C7SM00874K
Citation: Soft Matter, 2017,13, 5724-5730
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    Dielectrophoretic assembly of dimpled colloids into open packing structures

    Z. Jia, S. Sacanna and S. S. Lee, Soft Matter, 2017, 13, 5724
    DOI: 10.1039/C7SM00874K

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