New meaning to "magnetic" stirring

A new approach to using magnetism for mixing provides a simple and robust way to achieve instantaneous and homogeneous mixing at any scale, say its developers at Sandia National Laboratories, Albuquerque, N.M. The technique avoids agitators or other mechanical parts contacting fluid. Instead, it relies on magnetizable particles suspended in the fluid forming chains and then swirling to create effective mixing throughout the fluid. When mixing is done, a magnet can quickly and completely remove the particles, which can be reused, notes Jim Martin, a materials scientist at Sandia.

The method, called vortex field mixing, subjects particles to a rotating magnetic field with a precession-like motion. This causes the particles to assemble into a multitude of microscopic chains that follow the field motion and stir the entire volume of fluid regardless of the complexity its shape (Figure 1). (A YouTube video showing the mixing can be downloaded via http://www.youtube.com/watch?v=_2izq-XOvlg.)