Abstract.
In spite of its metastability, the pseudo-planar texture of a nematic layer confined between surfaces with homeotropic anchoring can be preserved indefinitely in certain conditions. The pseudo-planar texture, dubbed “the dowser texture”, is degenerated and therefore sensitive to perturbations. It has been shown recently that the dowser texture is cuneitropic, that is to say, has a tendency to follow thickness gradients. Here, we point out that the dowser texture is also rheotropic or, in other words, has a weathercock behavior: it tends to follow the direction of Poiseuille flows. We observed this behavior in two experiments. In the first one it appears as a deformation of a wound up dowser texture submitted to a slowly alternating linear Poiseuille flow. In the second one we study rheotropic effects of elliptical flow patterns generated by modulation of the gap thickness in a system made of a rigid lens and a flexible glass slide. We show that such elliptical flows can wind the dowser texture and therefore can be used in studies of generation and annihilation of nematic monopoles.
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Pieranski, P., Hulin, JP. & Godinho, M.H. Rheotropism of the dowser texture. Eur. Phys. J. E 40, 109 (2017). https://doi.org/10.1140/epje/i2017-11598-0
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DOI: https://doi.org/10.1140/epje/i2017-11598-0