Measurement of the continuous Lehmann rotation of cholesteric droplets subjected to a temperature gradient

Patrick Oswald; Alain Dequidt

doi:10.1103/PhysRevLett.100.217802

Measurement of the continuous Lehmann rotation of cholesteric droplets subjected to a temperature gradient

Patrick Oswald ¹ Alain Dequidt ¹

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

Abstract : In 1900, Otto Lehmann observed the continuous rotation of cholesteric drops when subjected to a temperature gradient. This thermomechanical phenomenon was predicted 68 years later by Leslie from symmetry arguments but was never reobserved to our knowledge. In this letter, we present an experiment allowing quantitative analysis of the Lehmann effect at the cholesteric-isotropic transition temperature. More precisely, we measure the angular velocity of cholesteric drops as a function of their size and the temperature gradient and we show that applying an electric field can stop the drop rotation. From these observations and a theoretical model we estimate the Lehmann coefficient.

Keywords : Cholesteric liquid crystal Thermomechanical coupling Lehmann effect

Type de document :

Article dans une revue

Physical Review Letters, American Physical Society, 2008, 100 (21), pp.217802. 〈10.1103/PhysRevLett.100.217802〉

Domaine :

Physique [physics] / Matière Condensée [cond-mat] / Matière Molle [cond-mat.soft]

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https://hal-ens-lyon.archives-ouvertes.fr/ensl-00351675
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