Fluid Flow

At its annual meeting last fall, the American Physical Society's Division of Fluid Dynamics selected a short video by Markus Zahn, professor of electrical engineering, and Cory Lorenz '03 as one of five winning entries in its Gallery of Fluid Motion. The video, which captures the pair's discovery of a ferrofluid's unusual ability to flow into complex designs, will be featured in the September 2003 issue of Physics of Fluids. It will appear alongside the other winning entries, which include a video by mechanical engineering professor Gareth McKinley, PhD '91, and a poster by associate math professor John Bush.

The gallery was an assemblage of 25 poster and video entries that demonstrate fluid flow phenomena. Entries were judged on such criteria as originality, the ability to convey information, and artistic content.

Zahn and Lorenz's groundbreaking video shows a drop of ferrofluid-liquid containing magnetic particles-that has been placed between two glass disks. The liquid, which is normally stable, responds to magnetic attraction. When Zahn and Lorenz apply two magnetic fields, the drop changes shape to resemble cartoonlike doodles.

At the meeting, Zahn observed attendees' reactions to the video. "You could hear people under their breath go, Wow,'" he says.

Ferrofluids are commonly used as sealants on computer disk drives to keep out dust. However, Zahn '67, SM '68, EE '69, ScD '70, is currently working with several students to apply this research to microfluidic and microelectromechanical devices, and to understand why the ferrofluid forms such intricate patterns under these conditions.