Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 3: SYMPOSIUM: Dynamics of multi-component fluids III

CPP 3.4: Talk

Friday, March 4, 2005, 15:00–15:15, TU C243

Juggling with Droplets: Digital Microfluidics — •Craig Priest, Dmytro Melenevsky, Stephan Herminghaus, and Ralf Seemann — MPI for Dynamics and Self-Organization, D-37073 Göttingen

Microfluidics is usually concerned with single phase liquids transported along solid microchannels. We explored to use emulsions as compartmented liquids instead of a single phase flow. If the continuous phase has a very small volume fraction, the emulsion is geometrically quite analogous to a foam and the position of each liquid compartment in the arrangement is well defined, provided all compartments have about the same size. The main issue here is the interplay of the internal length scale of the fluid, i.e., the size of the liquid compartments (droplets), with the lateral dimension of the channels. While it is well known from millimetre scale foam that this interaction is very well defined, a major question concerns the scalability of this concept to the micron regime. As a first approach, we produced emulsions in situ on the length scale of several 100 microns in a microfluidic device. We exploited the mentioned possibility of manipulation of the droplets by the channel geometry for positioning, sorting, exchanging, compiling and redistributing them. We furthermore demonstrated the possibility of merging droplets and inducing chemical reactions within compartments with different chemical contents. This may be called digital microfluidics, and will be well suited for applications in combinatorial chemistry, DNA sequencing, drug screening, and any other field where many similar chemical reactions have to be induced with minute amounts of substance.