Monodisperse Emulsion Generation via Drop Break Off in a Coflowing Stream

Using work published by the Weitz Group as a guide, I built a machine that produces highly monodisperse emulsions.

The phase that the droplets will consist of is introduced via a tapered capillary into a coflowing continuous phase that is full of surfactant. Droplets detach from the capillary when the streamwise forces from the flowing phase exceed the force from interfacial tension. Emulsions composed of a variety of fluids, including metal, and with drop sizes ranging from 2 to 200 μm have been produced using this technique.

Droplets & Emulsions

Various pictures of droplets
Various optical micrographs of emulsions taken by Jing Xhou. The emulsions were made using my droplet machine.

Metal Spheres

Using the droplet machine, but molten metal instead of water, former graduate student Chris Knutson was able to produce monodisperse metal spheres. He used these metal spheres in various experiments in order to study their various electric properties, including charge shuttling, self-assembly of wires, and more. I only helped make the samples seen in the following pictures, while Chris took the pictures himself.


Many same-size metal spheres. The image on the right gives us a closer look, showing how reflective their surfaces are. Nifty!


Self-assembled metal wires.

With the application of an electric field, we are able to produce self-assembling wires. Another unique property of these wires is that with the continued application of an electric potential the wires are self-healing.


References

Umbanhowar, P. B., V. Prasad, et al. (2000). "Monodisperse Emulsion Generation Via Drop Break Off in a Coflowing Stream." Langmuir 16: 347-351

Gi-Ra Yi, David J. Pine, et al. (2002), "Monodisperse Micrometer-scale Spherical Assemblies of Polymer Particles" Advanced Materials, 14, 1137-1140

Publications

C. R. Knutson, K. V. Edmond, M. T. Tuominen, A. D. Dinsmore,"Shuttling of Charge by a Metallic Sphere in Viscous Oil" (submitted, 2006).