Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Wetting, Micro- and Nanofluidics

CPP 44.9: Talk

Thursday, March 14, 2013, 17:45–18:00, H39

Droplet morphologies in a cylindrical tube — •Ciro Semprebon, Stephan Herminghaus, and Martin Brinmann — Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

Equilibrium conformations of droplets on cylindrical fibers and their transitions during changes of volume and contact angle have been studied for almost a century. Liquid morphologies in a tube, however, have received only little attraction. Here, we present the results of a combined analytical and numerical study of droplet shapes wetting the inside of a cylinder at zero buoyancy. For any contact angle the liquid forms a plug bounded by two spherical surfaces if the volume is sufficiently large. In the opposite limit of small volumes, the liquid interface adopts the shape of a spherical cap which is slightly deformed by the curved surface. At intermediate volumes and small contact angle an annular morphology is observed which can be described as the analog to the barrel droplet on a fiber. In contrast to the barrel droplets the mechanical stability of this morphology is limited by the appearance of either an axisymmetric or a non-axisymmetric soft mode. Stability with respect to the latter type of mode can be related to the existence of an inflection point in the droplet contour as already demonstrated for barrel droplets [1]. Based on our findings a complete morphology diagram is constructed in terms of contact angle and volume.

[1] H B Eral et al.: "Drops on functional fibers: from barrels to clamshells and back" Soft Matter 7 (2011) 5138