Issue 12, 2009

Dynamic charge separation in a liquid crystalline meniscus

Abstract

Oscillating electric fields can sustain a macroscopic and steady separation of electrostatic charges. The control over the dynamic charge separation (dyCHASE) is presented for the example of circular menisci of thin, free standing smectic films. These films are subject to an in-plane, alternating radial electric field. The boundaries of the menisci become charged and unstable in the electric field and deform into pulsating, flower-like shapes. This instability ensues only at frequencies of the electric field that are lower than a critical one. The critical frequency is a linear function of the strength of the electric field. Since the speed of electrophoretic drift of ions is also linearly related to the strength of the field, the linear relation between critical frequency and the amplitude of the field sets a characteristic length scale in the system. We postulate that dyCHASE is due to (i) electrophoretic motion of ions in the liquid crystalline (LC) film, (ii) microscopic separation of charges over distances similar in magnitude to the Debye screening length, and (iii) further, macroscopic separation of charges through an electro-hydrodynamic instability. Interestingly, the electrophoretic motion of ions couples with the macroscopic motion of the LC material that can be observed with the use of simple optical microscopy.

Graphical abstract: Dynamic charge separation in a liquid crystalline meniscus

Supplementary files

Article information

Article type
Paper
Submitted
07 Jul 2008
Accepted
16 Oct 2008
First published
18 Nov 2008

Soft Matter, 2009,5, 2352-2360

Dynamic charge separation in a liquid crystalline meniscus

T. Szymborski, O. Cybulski, I. Bownik, A. Żywociński, S. A. Wieczorek, M. Fiałkowski, R. Hołyst and P. Garstecki, Soft Matter, 2009, 5, 2352 DOI: 10.1039/B811561C

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