The focus of the research has been on producing tiny batteries for powering MEMS and which, in theory, could last thousands of years. While radioisotope batteries have previously been used in spacecraft, the new batteries are much smaller and utilize a liquid semiconductor as opposed to traditional solid state devices used in nuclear batteries. The battery's output is 16.2nW.The research has been undertaken by Prof "Jae Kwon" and J "David Robertson" from the University of Missouri. Robertson said: "The hard part of using radioactive decay is that when you harvest the energy, part of that energy goes towards creating defects that damage a solid state semiconductor. So we created a battery without that part degrading over time. "Prof Kwon added that he believes that the nuclear liquid semiconductor power units could eventually be made 'thinner than a human hair'