THE CUTTING EDGE : SCIENCE WATCH : Researchers Looking to Nuclear Energy to Power Tiny Devices

Try this one on for size: Nuclear power on a chip.

Researchers around the world are developing devices smaller than the width of a human hair for all sorts of uses ranging from biochemical sensors to medical implants.

But here’s the hang-up. Nobody has been able to come up with a power source small enough to be compatible with such tiny micromechanical devices.

Anyone who has lugged around a 1-pound laptop with a 5-pound battery should get the drift here. To realize their full potential, these devices need a power source that can deliver a real punch but still be small enough to fit on the same chip.

Now, a team of engineers at the University of Wisconsin in Madison believe they may be on the right track. They have just started a program to use nuclear energy as a source of power, but these generators would bear little resemblance to the domed power plants that feed electricity into homes and factories.

Instead of turning turbines to generate electricity, these minuscule devices would use a tiny speck of radioactive material to produce electricity through radioactive decay. It’s been done before, but on a much larger scale, for devices ranging from heart pacemakers to spacecraft that probe the dark reaches of the outer solar system.

“It’s never been done at the scale we are talking about,” said James Blanchard, professor of nuclear engineering at the University of Wisconsin. He is a leader of the team that is trying to develop the technology. The work is sponsored by a $450,000 grant from the Department of Energy.

Although the mere mention of nuclear power sends chills up the backs of some, the researchers say their generators will use so little radioactive material that safety should not be an issue. Blanchard said the element that would seem to lend itself best to the process is polonium, discovered in 1898 by Marie and Pierre Curie.

Radioactive material is already in use in many devices, including smoke detectors, and some photocopiers use a strip of radioactive material to eliminate the static charge in sheets of paper.

But to work as a power source for tiny “machines” of the future, the technology must be scaled down to a microscopic level.

Blanchard said radioactive material can be used to generate electricity in two ways. Heat given off by radioactive decay can cause some materials to emit electrons, thereby creating electricity. But the team is leaning toward a more direct approach.

“When a radioactive isotope decays it emits a charged particle, so you can just directly capture those charged particles and create electricity,” Blanchard said. Those particles can generate very high voltages relative to the size of the device, he added.

Blanchard said his team is not directly concerned with the application of the device. Once an adequate power supply is available, he said, others will come up with many uses. In fact, scores of labs around the world are already creating micro-electromechanical structures, called MEMS, one of the hot-button subjects in high tech today.

Once the power is available, that will lead to “applications that have never been possible,” according to electrical engineering professor Amit Lal, Blanchard’s colleague on the project.

The most immediate application will likely be in the development of a wide range of tiny sensors. An adequate power source could link hundreds of small sensors through wireless communications, a potential use that has military implications.

Such sensors, too small to be seen, could detect the presence of chemicals in a hostile environment.

“If they sense a chemical that they don’t like, they could send a signal back to some central location so people could look for these chemical weapons without having to be present,” Blanchard said.

They could also be used to detect microscopic levels of hazardous chemicals and gases in industrial plants.

One interesting possibility is to make the sensors so small they could actually be mixed into grease used in heavy machinery to detect when maintenance is required.

“The biggest impact could be in making everyday systems more reliable, safer and smarter by integrating these sensor systems,” Lal said.

The general technology is well understood. The challenge facing the university’s team is to bring it down to a scale that is much, much smaller than anyone else has been able to do.

Lee Dye can be reached at [email protected].