Abstract
The electrohydrodynamic (EHD) vortices produced by an electric current in freely suspended liquid crystal (LC) films of N-(4-methoxybenzylidene)-4-butylaniline (MBBA), convert to a pure rotation in the presence of external electric field (\(\it{E}_{{\rm ext}}\)) perpendicular to the current direction. Here, the direction and strength of the rotation are precisely under control by our self-made device called “liquid-film motor”. In this paper, we present experimental observations of the EHD fluid flow when external electric field varies from zero to a value in which pure rotation on the liquid crystal (LC) film is observed. We also show experimentally that the presence of external electric field causes a great decrease in the current produced by the voltage V J required for observing EHD vortices in freely suspended films of MBBA. The LC films begin to rotate when E ext V J reaches a threshold value. This threshold is investigated experimentally as a function of voltage V J and the external electrical field \(\it{E}_{{\rm ext}}\).
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Notes
Movies are available from http://www.softmatter.cscm.ir/FilmMotor.
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Acknowledgments
This work is funded by Applied Physics Research Center of Sharif University and the experiments were performed at the Medical Physics Laboratory of Physics Department. We thank Prof. S. W. Morris for his guides at the initial stage of this work, Dr. A. Nejati for his useful discussion and revision and Dr. A. Tonddast-Navaei for his PIV software. We also thank A. Mahdavi and M. Sadeghi for their technical helps and useful discussions.
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Shirsavar, R., Amjadi, A., Ejtehadi, M.R. et al. Rotational regimes of freely suspended liquid crystal films under electric current in presence of an external electric field. Microfluid Nanofluid 13, 83–89 (2012). https://doi.org/10.1007/s10404-012-0943-5
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DOI: https://doi.org/10.1007/s10404-012-0943-5