Research Papers: Techniques and Procedures

Parallel-Plate Conductive Electrodes for the Fabrication of Larger 2D Colloidal Photonic Crystals

[+] Author and Article Information
R. Asmatulu

Department of Mechanical Engineering, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0133

S. Kim, F. Papadimitrakopoulos

Nanomaterials Optoelectronics Laboratory, Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136

H. Marcus

Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136

J. Fluids Eng 131(5), 051401 (Apr 14, 2009) (5 pages) doi:10.1115/1.3111257 History: Received April 20, 2008; Revised September 22, 2008; Published April 14, 2009

A new dielectrophoretic force-induced parallel-plate assembly technique was used to achieve close-packed 2D large colloidal photonic crystals on gold electrodes (200nm thick). The electrodes were patterned on a glass substrate using a conventional UV lithography technique. The experimental tests conducted with 5.3μm carboxyl functionalized polystyrene particles at various ac and dc voltages, frequencies, and particle concentrations showed that larger size (0.25×3mm2) colloidal photonic crystals were fabricated on the ground electrode rather than on the working electrode. To date, this is the largest colloidal photonic crystal fabricated using this method. The reason behind this phenomenon can be attributed to the electro-osmotic flow in the colloidal system and dipole-dipole attractions between the colloidal particles.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Schematic outline of the experimental procedure (left) utilized to assemble larger 2D colloidal photonic crystals on the parallel-plate gold electrodes (right) connected to a power supplier. The red line is the working electrode, while the dark line is the ground electrode on which the photonic crystals were formed (not to be scaled).

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Figure 2

Photographs showing (a) particles settled after 30 min, and crystallized forms at (b) 0.1 dc V and (c) 0.5 dc V on top of the ground electrodes. Note that the white parts show the gold substrate surface, while the dark stripes show the glass substrate with the PS particles decorating the gold surfaces.

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Figure 3

Photographs showing (a) parallel-plate gold electrode (white parts) patterned on a glass substrate (dark parts), (b) particles settled on the surface, and (c) colloidal particle localized crystallization at 0.4 dc V

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Figure 4

Photographs showing (a) larger colloidal photonic crystal collected on the electrodes and (b) crystallization at 2 ac V, 1 MHz frequency, 0.5% solid content, and pH 8

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Figure 5

Photographs illustrating (a) PS particles settled on the electrodes; (b) parallel-plate DEP tests conducted at 2 ac V, 1 MHz, pH 8.0, and 0.2% solid content; and (c) formation of pearl chains between the electrodes and second layer on the first layer of the crystal on the ground electrode at 4 ac V and 0.5% solid content

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Figure 6

Crystallization of larger colloidal photonic particles (a) after settlement on the electrodes under (b) 0.4 dc V, and (c) both 0.4 dc and 3 ac V with 1 MHz. This is the largest known colloidal PC to date.

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Figure 7

Photograph illustrating the remaining colloidal particles in mostly crystalline form after washing several times with DI water

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Figure 8

Schematic illustrations of larger colloidal particle crystallization under dc followed by dc/ac electric fields



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