Droplets in External fields

Electric fields in microfluidic channels provides additional level of control on droplet actuation. In electric field, droplets can be actuated at the submillisecond time-scale without the use of mechanical parts. Besides actuation mechanisms, electric fields are used to perturbate the equilibrium of droplet interfaces and initiate droplet coalescence by an electro-hydrodynamic instability of the oil layer between conducting droplets.


System Integration: Electric fields and Droplet-based microfluidics

We integrate small and compact electric systems to apply electric fields in microchannels. Such systems with a small footprint will be the basis for compact and stand alone systems usable for droplet coalescence or sorting.

Fluorescence Activated Droplet Sorter (FADS)

The interactions between fluids, interfaces and electric fields lead to a very rich range of phenomenae that can be used - for example - to actuate droplets in microchannels. Here, we use dielectrophoretic forces to actuate droplet in one channel or another at a Y-junction. The field can be triggered on the fluorescence readout of the droplet, providing tools to select specific droplet in a droplet population. We demonstrate the potential of the technique on the separation of bacterial cells as a function of their enzymatic activities, revealed by a fluorogenic assay. Our system is analogous to a Fluorescence-Activated Cell Sorter (FACS), except that droplets are manipulated and sorted, which enables the selection of micro-organisms as a function of a secreated enzyme or compound, which is not doable in standard FACS systems. The use of a microfluidic-based system also provides the basis to integrate more complex operations, as droplet fusion and mixing or long-term incubation in micro-compartments.

Related PhD Thesis in the Group

Related Publications

Fluorescence-activated droplet sorting (FADS): efficient microfluidic cell sorting based on enzymatic activity
J.-C. Baret, O. J. Miller, V. Taly, M. Ryckelynck, A. El-Harrak, L. Frenz, C. Rick, M. L. Samuels, J. B. Hutchison, J. J. Agresti, D. R. Link, D. A. Weitz, and A. D. Griffiths
Lab Chip 9, 1850 (2009)
Self-excited drop oscillations in electrowetting
J.-C. Baret, M. M. J. Decre and F. Mugele
Langmuir 23, 5173 (2007)

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