In the late 1960s Medtronic – today the largest manufacturer of implantable medical devices in the world – teamed up with Alcatel, a French company, to design a nuclear-powered pacemaker. The first human implant of the device took place in Paris in 1970.
The nuclear battery in the Medtronic device used a tiny 2.5 Ci slug of metallic Plutonium 238 (Pu-238). The radiation produced by the Pu-238 bombarded the walls of its container, producing heat that a thermopile then converted to an electrical current. A thermopile is a stack of thermocouples, which are devices that convert thermal energy directly into electrical energy using Seebeck effect. A thermocouple is made of two kinds of metal (or semiconductors) connected to each other in a closed loop. If the two junctions are at different temperatures, an electric current will flow in the loop. Continue reading