Nonlinear electrophoresis of dielectric and metal spheres in a nematic liquid crystal
Oleg D. Lavrentovich1, Israel Lazo1 & Oleg P. Pishnyak1
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
Correspondence to: Oleg D. Lavrentovich1 Email: email@example.com
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Electrophoresis is a motion of charged dispersed particles relative to a fluid in a uniform electric field1. The effect is widely used to separate macromolecules, to assemble colloidal structures and to transport particles in nano- and microfluidic devices and displays2, 3, 4. Typically, the fluid is isotropic (for example, water) and the electrophoretic velocity is linearly proportional to the electric field. In linear electrophoresis, only a direct-current (d.c.) field can drive the particles. An alternating-current (a.c.) field is more desirable because it makes it possible to overcome problems such as electrolysis and the absence of steady flows5, 6. Here we show that when the electrophoresis is performed in a liquid-crystalline nematic fluid, the effect becomes strongly nonlinear, with a velocity component that is quadratic in the applied voltage and has a direction that generally differs from the direction of linear velocity. The new phenomenon is caused by distortions of the liquid-crystal orientation around the particle that break the fore–aft (or left–right) symmetry. The effect makes it possible to transport both charged and neutral particles, even when the particles themselves are perfectly symmetric (spherical), thus allowing new approaches in display technologies, colloidal assembly and separation, microfluidic and micromotor applications.