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Related Experiment Video

Updated: Jul 11, 2026

An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation
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Does the electric Lehmann effect exist in cholesteric liquid crystals?

A Dequidt1, P Oswald

  • 1Laboratoire de Physique, Ecole Normale Supérieure de Lyon, Lyon, France. alain.dequidt@ens-lyon.fr

The European Physical Journal. E, Soft Matter
|October 11, 2007
PubMed
Summary

This study challenges the electric Lehmann effect, showing that flexoelectricity better explains the motion of cholesteric liquid crystals under electric fields. Experimental results indicate no clear evidence for the electric Lehmann effect currently.

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Area of Science:

  • Liquid Crystal Physics
  • Soft Matter Science
  • Electromagnetism

Background:

  • Cholesteric liquid crystals exhibit motion under electric fields, previously explained by the electric Lehmann effect.
  • Alternative electrohydrodynamic explanations have emerged, questioning the electric Lehmann effect's validity.
  • Prior experiments by Padmini and Madhusudana supported the electric Lehmann effect in compensated cholesteric liquid crystals.

Purpose of the Study:

  • To re-evaluate the electric Lehmann effect's applicability to cholesteric liquid crystal motion.
  • To investigate the behavior of cholesteric liquid crystals in planar and pi-twisted planar geometries.
  • To explore alternative physical mechanisms, such as flexoelectricity, for observed phenomena.

Main Methods:

  • Replication of Padmini and Madhusudana's experiment with compensated cholesteric liquid crystals.
  • Extension of experiments to a pi-twisted planar geometry.
  • Analysis of experimental results to determine compatibility with the electric Lehmann effect and flexoelectricity.

Main Results:

  • Experimental results align with Padmini and Madhusudana's findings in the planar geometry.
  • The observed phenomena in both planar and pi-twisted geometries are incompatible with the electric Lehmann effect.
  • Flexoelectricity provides a consistent explanation for the entire data set across both geometries.

Conclusions:

  • The electric Lehmann effect is unlikely to be the primary mechanism driving the observed motion in cholesteric liquid crystals.
  • Flexoelectricity offers a more comprehensive and accurate explanation for the electrohydrodynamic behavior of these materials.
  • Current experimental evidence does not support the existence of the electric Lehmann effect.