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Micromachines 2019, 10(1), 45;

Liquid Crystals-Enabled AC Electrokinetics

Department of Physics and Materials Science, The University of Memphis, Memphis, TN 38152, USA
Department of Physics and Chemical Physics Interdisciplinary Program, Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA
Authors to whom correspondence should be addressed.
Received: 12 December 2018 / Revised: 1 January 2019 / Accepted: 1 January 2019 / Published: 10 January 2019
(This article belongs to the Special Issue AC Electrokinetics in Microfluidic Devices)
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Phenomena of electrically driven fluid flows, known as electro-osmosis, and particle transport in a liquid electrolyte, known as electrophoresis, collectively form a subject of electrokinetics. Electrokinetics shows a great potential in microscopic manipulation of matter for various scientific and technological applications. Electrokinetics is usually studied for isotropic electrolytes. Recently it has been demonstrated that replacement of an isotropic electrolyte with an anisotropic, or liquid crystal (LC), electrolyte, brings about entirely new mechanisms of spatial charge formation and electrokinetic effects. This review presents the main features of liquid crystal-enabled electrokinetics (LCEK) rooted in the field-assisted separation of electric charges at deformations of the director that describes local molecular orientation of the LC. Since the electric field separates the charges and then drives the charges, the resulting electro-osmotic and electrophoretic velocities grow as the square of the applied electric field. We describe a number of related phenomena, such as alternating current (AC) LC-enabled electrophoresis of colloidal solid particles and fluid droplets in uniform and spatially-patterned LCs, swarming of colloids guided by photoactivated surface patterns, control of LCEK polarity through the material properties of the LC electrolyte, LCEK-assisted mixing at microscale, separation and sorting of small particles. LC-enabled electrokinetics brings a new dimension to our ability to manipulate dynamics of matter at small scales and holds a major promise for future technologies of microfluidics, pumping, mixing, sensing, and diagnostics. View Full-Text
Keywords: liquid crystal; electrophoresis; electro-osmosis; alternating current (AC) electrokinetics liquid crystal; electrophoresis; electro-osmosis; alternating current (AC) electrokinetics

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Peng, C.; Lavrentovich, O.D. Liquid Crystals-Enabled AC Electrokinetics. Micromachines 2019, 10, 45.

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