Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Poster: Wetting, Micro and nanofluidics

CPP 21.17: Poster

Wednesday, March 28, 2012, 11:00–13:00, Poster A

Microfluidic systems for surface tension measurement — •Quentin Brosseau and Jean-Christophe Baret — Max Planck Institut for Dynamics & Self-organization, Göttingen, Germany

With the increasing number of microfluidics droplet-based methods developed, understanding surfactant adsorption at droplet interfaces, as main stabilizing process of emulsions, has become a major concern. Although such processes are well described in the diffusional case, models does not apply on chip where convective circulation is present. Our project aims at developing a series of microfluidic tools providing insights into the dynamics of surfactant adsorption, down to the millisecond-scale, for a dynamic determination of droplets surface tension. We for example exert a localized hydrodynamic stress transversal to the flow direction on the droplet. The droplet response -- in deformation and relaxation -- is measured and studied. The measured droplet deformation profiles reveal the characteristic time for surfactant adsorption at the interface, and the adsorption-desorption equilibrium. The influence of surfactant concentration, both above and below the CMC, and of the liquid flow rate are measured and additional 2D numerical simulation of the droplet deformation profile, provide tools to link deformations to effective interfacial tension.