Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Micro and Nano Fluidics III: Migration and flow

CPP 28.3: Talk

Thursday, February 28, 2008, 17:15–17:30, C 264

Positive and negative diffusive-like migration of particles using ion specific effects in microchannels — •Lyderic Bocquet¹, Benjamin Abecassis², Cecile Cottin-Bizonne², Christophe Ybert², and Armand Ajdari³ — ¹University of Lyon and Technical University Munich — ²University of Lyon — ³ESPCI, Paris - Saint-Gobain

Developing versatile methods for driving and manipulating macromolecules or biological cells in microchannels is a key challenge for lab-on-a-chip devices. State of the art approaches for particles' manipulation usually require external fields or specifically designed channel geometries. Here we present a passive and very simple method leading to a tunable and efficient migration of particles in the absence of any external field. Using this method the particles are shown to exhibit a diffusive-like motion which is strongly amplified compared to their bare diffusion process. Moreover both spreading and focusing of the particle assembly can be achieved on demand, corresponding to positive or negative diffusive-like migration. While focusing is a priori conflicting with the second law of thermodynamics, it is obtained in the present mechanism by slaving the particle's dynamics to a fast carrier specie, here a dilute salt, via a chemotaxis-like transport phenomenon, diffusio-phoresis. As a proof of principle, both homogeneization and focusing of a colloidal solution in a microchannel are demonstrated, illustrating the potential of this versatile method for microfluidic applications.