NIST logo

Publication Citation: Multiple electrokinetic actuators for feedback control of colloidal crystal size

NIST Authors in Bold

Author(s): Jaime Juarez; Pramod P. Mathai; James A. Liddle; Michael Bevan;
Title: Multiple electrokinetic actuators for feedback control of colloidal crystal size
Published: July 27, 2012
Abstract: We report a feedback method for controlling the sizes of hexagonally close packed two-dimensional colloidal crystals in a microfluidic quadrupole electrode device. Crystal size, measured by the number of colloidal particles comprising the crystal, is controlled over an order of magnitude range with a variation of less than 10% for colloidal crystals containing 20 to 250 micron-sized silica spheres. The total number of particles in the control region is tracked in real time and alternating applications of electrokinetic mechanisms ‹ either electro-osmosis or negative dielectrophoresis ‹ are actuated to guide the formation of the crystals of the targeted size. Subtle changes in the bounding geometry of the crystal compare well with scaling models of the number of particles on the crystal edge and a geometrical parameter reflecting the degree of hexagonal close packing. This model system gives us the opportunity to explore concepts relevant to the controlled assembly of nanoscale objects for nanomanufacturing.
Citation: Lab on A Chip
Volume: 12
Issue: 20
Pages: pp. 4063 - 4070
Keywords: feedback control, crystal assembly, dielectrophoresis, electroosmotic flow
Research Areas: Directed self-assembly
DOI: http://dx.doi.org/10.1039/c2lc40692f  (Note: May link to a non-U.S. Government webpage)
PDF version: PDF Document Click here to retrieve PDF version of paper (1MB)