Micro Flow Control Group

The focus of this work is to understand the physics behind spontaneous dispersion of particles when they come in contact with a fluid-fluid interface (see the figure below). We have recently shown:

• that this can cause particles sprinkled over a small area to spread almost instantaneously over an area that is several orders of magnitudes larger;
• a dropped particle causes particles already trapped on the interface to move away, creating a particle-free region around a newly-adsorbed particle; and
• influence the nature of monolayer clusters, e.g., porosity, on interfaces that are formed.

These phenomena have importance in a wide range of applications, such as pollination in hydrophilous plants, flotation and spreading of viruses and nanoparticles, self-assembly of micron- to nano-sized particles, stabilization of emulsions, etc. While the focus of the past studies has been on understanding the mechanisms by which particles already trapped on fluid-fluid interfaces interact leading to their self assembly into monolayered patterns, the sudden dispersion of particles coming into contact with a fluid-fluid interface which is being investigated has not been previously considered.

Figure. Sudden dispersion of sand particles sprinkled onto water in a Petri dish. Notice the streak lines formed due to the radially-outward motion of the particles emanating from the location where they were sprinkled.

Dispersion