London: An implantable pacemaker as tiny as a pinhead is set to revolutionise medicine with its big advantage. It is powered by radio waves from outside the body and does not need batteries.

The breakthrough by Stanford University engineers could lead to a host of new medical sensors that could function without batteries. The implanted device is housed in a cube less than a millimetre in radius.

Millions of pacemakers, cochlear implants and drug pumps are today helping people live relatively normal lives, but these devices are not without engineering challenges. First off, they require power, which means batteries. And batteries are bulky, the journal "Applied Physics Letters" reports.

In a pacemaker or a similar device, the battery alone accounts for as much as half the volume of the device it powers. Second, batteries have limited lives. New surgery is needed when they are spent, according to the "Daily Mail".

"Wireless power solves both challenges," said Ada Poon, professor of electrical engineering at Stanford, who led the research. Last year, Poon made headlines when she demonstrated a wirelessly powered, self-propelled device capable of swimming through the bloodstream.

Beyond the heart, they believe such devices might include swallowable endoscopes-so-called "pillcams" that travel the digestive tract, permanent pacemakers and precision brain stimulators. The new device could power virtually any medical application where size and power matter.