Embedded rotors mix fluids

Researchers from Curie Institute in France and the Max Planck Institute in Germany have found that it is possible to change the way fluid flows through arrays of tiny rotary motors embedded in a membrane.

Minuscule motor arrays could eventually be used to sort, mix and transport molecules for medicine, biology and bioengineering applications.

The researchers worked out the collective effects of membrane-embedded rotary motors made from natural molecules powered by the ATP molecule that drives biological processes. Each motor powers itself, but is also subject to the forces of the fluid pushed by other motors.

According to the researchers' calculations, when enough ATP is present to cause the motors to move at high speeds, the flows produced by the motors interact to form a triangular lattice much like the atomic structure of a crystal. At lower concentrations of fuel, the motors enter a disordered phase that causes random motion.

The two phases, and resulting flows, affect liquids differently. The disordered phase, for instance, is more effective at defusing, or mixing.

Such flows are probably important to biological systems, and could be exploited to transport molecules at the nanoscale, according to the researchers.

It will take at least 10 years the motors are ready for use in practical applications, according to the researchers. The work appeared in the September 5, 2003 issue of Physical Review Letters.