Inventors of the tiniest machines have tapped various power sources for their devices: electricity, light, even DNA. Now, Amit Lal of Cornell University and his colleagues are fueling a tiny oscillating cantilever with nuclear energy.
Because a single load of nuclear fuel can last a half-century or more, the devices might serve as microsensors on long, lonely jobs such as monitoring stockpiled missiles, Lal says. The researchers are now adapting the cantilever to drive a rotary motor, he adds.
The device, which works only in a vacuum, gets power from nuclear decay within a film of radioactive nickel-63. As the nickel decays, ejected electrons embed themselves in the gold-plated tip of a nearby strip of silicon nitride only two micrometers thick. As that strip builds negative electric charge, it bends toward the increasingly positive nickel. When the surfaces get close together, a flow of electric current wipes out the charge disparity. The strip then springs back and restarts the cycle.
Months ago, while Lal was at the University of Wisconsin–Madison, he and his colleagues developed a larger, copper prototype of the cantilever described in the July 15 Journal of Applied Physics. Lal unveiled the microdevice Aug. 7 in Detroit at a meeting organized by the Defense Advanced Research Projects Agency, one of the funders of the research.