Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster: Micro- and Nanofluidics

CPP 35.24: Poster

Wednesday, March 16, 2011, 17:00–19:00, P2

Droplet-based microfluidic systems for dynamic surface tension measurements — •Quentin Brosseau and Jean-Christophe Baret — Max Planck Institute for Dynamics and Self-organization

The accurate characterization and the control of interfaces is of primary importance for various fields of research, from material sciences to cell biophysics. Although surface tension -- one key parameter to describe interfaces -- is a concept well defined for interfaces between pure liquids or in static conditions, many question arise with the dynamics of adsorption of surfactant molecules at the interfaces [1,2] and we are facing a lack of tools to study these dynamic processes. Our aim is to develop new tools for measurement of dynamic surface tensions [2]. The idea is to produce and flow droplets in surfactant solutions through microchannel designed to induce deformations of the droplet. These deformations are controlled by the balance of viscous stress and the surface tension [3] and will allow dynamic measurement, down to millisecond time-scale. The measurements of the increase of droplet deformation with time, shows that the surface tension is decreasing along the microchannel. After a transient phase, a steady-state is reached in which surfactant is in dynamic equilibrium with the continuous phase. The characteristic time for this process is of the order of a few millisecond. By varying both the nature of surfactant and its concentration, we will look for universal behavior governing the build up of interfaces.

[1] J. Bibette, Emulsions: basic principles Rep. Prog. Phys., 62, 969 (1999); [2] J.-C Baret & al., Langmuir, 25(11), 6088 (2009); [3] J. Cabral & al., Lab Chip, 6, 427 (2006)