Researchers have demonstrated a penny-sized "nuclear battery" that produces energy from the decay of radioisotopes.

As radioactive substances decay, they release charged particles that when properly harvested can create an electrical current.

Nuclear batteries have been in use for military and aerospace applications, but are typically far larger.

The University of Missouri team says that the batteries hold a million times as much charge as standard batteries.

They have developed it in an attempt to scale down power sources for the tiny devices that fall under the category of micro- and nano-electromechanical systems (Mems and Nems).

The means to power such devices has been a subject of study as vigorous as the development of the devices themselves.