Amit Lal is looking for power-in doses small enough to run microscopic machines. The Cornell University electrical engineer and his colleagues have found a way to use nuclear energy to power such micro-electromechanical systems as those used for sensing or communications. Making batteries small enough to work with microscopic machines has been a challenge, but a speck of radioactive material, says Lal, could power such a device for more than 75 years. Lal’s system comprises a tiny copper cantilever that hovers above a thin film of radioactive nickel. The nickel emits electrons that hit the tip of the cantilever, causing it to deflect and swing back. This cyclical motion could be used to move a second mechanical component, or to generate electrical current. Using that current, nuclear-powered sensors embedded in the walls of buildings could run autonomously for decades, says Lal. He and his Cornell colleagues have started a company called Lifesonics in Ithaca, NY, to commercialize the technology. Lal hopes to have a prototype nuclear-powered temperature-and-pressure sensor ready within two years.