Tension gradients and Marangoni flows in nematic interfaces.
This brief report (i) presents equations that govern the balance of tangential forces in interfaces between isotropic viscous fluids and nematic liquid crystals, and (ii) establishes the physical origin of nematic Marangoni flows. It is shown that surface gradients in the orientation dependent surface free energy gives rise to tangential nematic Marangoni forces. Tangential nematic Marangoni forces are caused by surface gradients of the nematic tensor order parameter, and the kinetic coefficient characterizing this interfacial phenomenon is proportional to nematic elastic storage. Expressions of the Marangoni forces using a classical constitutive equation for the surface free energy are given for general and uniaxial nematic ordering states. Nematic Marangoni flows or nematocapillarity augments the class of Marangoni flows present in electrocapillarity, diffusocapillarity, and thermocapillarity.
Rey
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Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 2B2. inaf@musicb.mcgill.ca