Wee wires that can crawl.

While researchers today frequently create electronic and mechanical devices only a few nanometers in size, they can't easily manipulate those itty-bitty components. Now, an Israel-based team of chemists offers a possible solution: self-propelled nanowires.

Such mobile strands might switch electric current on and off in minuscule circuits by reversibly bridging gaps between other wires, says Fernando Patolsky. He and his colleagues at the Hebrew University of Jerusalem have also investigated such tiny itinerant wires as potential nano-transporters for hauling around chemicals within minute structures, including cells.

As reported in the October Nature Materials, the Jerusalem team made its active filaments by assembling threads of the muscle protein actin and then partially coating them with gold. When fueled with adenosine trisphosphate, or ATP, a common energy source in cells, the gold-plated actin strands crawled along a surface coated with a sister muscle protein called myosin.

Initially, the team couldn't direct which way the filaments went. The researchers acquired that capability by adding cobalt nanoparticles to the wires. "Now, by an external magnetic field, we can control where all the filaments move" notes Patolsky, currently of Harvard University.--P.W.