Tiny nuclear battery

University of Missouri engineers are building a nuclear battery the size of a penny. Their aim is to develop a long-lasting power source for tiny sensors, actuators, and labs-on-a-chip. While nuclear batteries sound, er, problematic, they're actually relatively common in larger form factors to power pacemakers and instruments aboard space vehicles. From MU News Bureau:
 News Stories 2009 Nuclear-Battery-Outstanding-At-Conference Images Microbattery-Edit Lg (Professor Jae Kown's) innovation is not only in the battery’s size, but also in its semiconductor. Kwon’s battery uses a liquid semiconductor rather than a solid semiconductor.

“The critical part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure of the solid semiconductor,” Kwon said. “By using a liquid semiconductor, we believe we can minimize that problem.”

In the future, they hope to increase the battery’s power, shrink its size and try with various other materials. Kwon said that the battery could be thinner than the thickness of human hair.
"MU Researchers Create Smaller and More Efficient Nuclear Battery"