Metal expands electrically

Researchers from Germany and Austria have found a way to make metal expand and contract like piezoceramics, which are commonly used as actuators in inkjet printers and automobile fuel injection nozzles. The expanding metal, however requires less voltage than piezoceramics.

The researchers made metal expandable by electrically adding or withdrawing electrons from metal surfaces. The method works in wet environments, and could eventually be used to power valves on labs-on-a-chip, or devices immersed in biological fluids in living systems, according to the researchers.

Key to the method was gaining a lot of surface area and thus access to more electrons by using clumps made from tiny bits of metal. The researchers used platinum crystals measuring less than 50 nanometers across to prove it is possible to change the material by injecting or withdrawing electrons. As they injected electrons, the bonds at the surface of the metal expanded, and when they withdrew electrons the bonds shrunk.

The researchers are from the Karlsruhe Research Center in Germany, University of Saarlandes in Germany, and the Technical University of Graz in Austria. The work appeared in the April 11, 2003 issue of Science.