Droplets and bubbles

Microfluidic systems offer perfect control over formation of both bubbles and droplets. Practically all important characteristics of the foams or emulsions that are formed in the microsystems can be precisely tuned. In the simplest applications it is important to control the volume of the bubbles [1] or droplets [2,3], the volume fraction that they occupy [1] and also the frequency at which they are formed [1]. It is also possible to form dispersions with more than one size of their constituents: from bimodal, through multimodal dispersions, with very narrow distribution of sizes around the individual modes, to dispersions with intricate (e.g. non Gaussian) continuous distribution of volumes [4]. Further, in systems comprising more than one dispersing unit, it is possible to prepare emulsions with a number of distinct families of droplets and/or bubbles of different sizes and different chemical composition, with the possibility of tuning the ratio of sizes of the constituents and their stoichiometry in such heterogeneous emulsions [5]. We currently study:

• new methods of formation of ultrasmall bubbles and droplets
• parallel systems for formation of bubbles and droplets
• the use of microfluidic emulsification techniques for formation of micro particles and capsules

[1] P. Garstecki, I. Gitlin, W. Diluzio, E. Kumacheva, H.A. Stone, G.M. Whitesides, Appl. Phys. Lett. 85, 2649 (2004)
[2] T. Thorsen, R. W. Roberts, F. H. Arnold, S. R. Quake, Phys. Rev. Lett. 86, 4163 (2001)
[3] S. L. Anna, N. Bontoux, H. A. Stone, Appl. Phys. Lett. 82, 364 (2003)
[4] P. Garstecki, M. Fuerstman, G.M. Whitesides, Nature Physics, 1, 168-171 (2005)
[5] M. Hashimoto, P. Garstecki, G.M. Whitesides, Small , 3, 1792-1802 (2007)