Nanofibers Evolving From Drop Break-up?

By Roland Piquepaille

Engineers and physicists working together have discovered that under certain conditions liquid drops and gas bubbles were breaking at two separate points instead of one, leaving an extremely thin thread in between. This could lead to the creation of nanofibers and nanowires and to numerous applications, such as new kinds of composite materials, electronic circuits and pharmaceutical products.

Nanotechweb.org reports on this discovery in "Nanowires drop out of fluid research."

There is a widely accepted universal rule that drops and bubbles always break away from a nozzle in the same way, no matter what the liquid or gas. As the drop forms, it is attached to the nozzle by a thin segment of liquid or gas. This segment grows thinner before breaking at a single point, allowing the drop to fall away from the nozzle.

But Osman Basaran of Purdue University and his colleagues have discovered an exception to the rule. While studying how liquid drops and gas bubbles are formed by nozzles such as those in inkjet printers, the researchers found that for a nozzle immersed in a viscous liquid such as silicone oil, water drops formed differently to the way they would in air. The drops formed much more slowly and the segment of liquid between the growing drop and the tip of the nozzle grew longer than it would in air, before cutting away from the nozzle at two points rather than one.

Here is an illustration showing how a water drop breaks up in oil, leaving a thin thread (Credit: Itai Cohen and Sidney R Nagel).

The liquid separated from the nozzle at both the place where the drop formed and at a point nearer to the nozzle. This left a drop of liquid, along with an extremely thin liquid thread.