Want to stop everyone in their tracks at a dinner party? Simply state that “users of future generations of mobile handsets could well be walking around with a nuclear-driven power source in their pockets.” A team of scientists at the University of Missouri in the U.S. has developed a battery about the size of a Euro coin that can be powered by energy generated by the decaying process of radioisotopes. Unquestionably, this technology could prove invaluable for use with future nanoscale- and MEMS-related technology, provided these batteries could be dramatically scaled down in size.
But before delving into the size issue, lets get back to that nuclear power in your pocket scenario. This may come as a disturbing revelation for some people, but it shouldn’t. Nuclear-powered batteries have been used for some years in applications where a long-term reliable source of electricity is a critical aspect. Heart pacemakers are an example.
In fact, it was almost 50 years ago that numerous designs were developed for nuclear-powered batteries. Amongst these were the nuclear thermal battery and the betavoltaic battery. In the latter, a semiconductor PN junction is exposed to electrons emitted by a radioactive substance. This, in turn, generates electricity.
Back in 2005, the University of Rochester announced the development of a 3D silicon diode fabricated in porous silicon. This greatly increases the PN junction surface area exposed to beta radiation from a tritium radioactive source.
The use of nuclear batteries in military applications is also well documented, but typically these are far larger than the battery that’s been demonstrated by Jae Wan Kwon and his team in Missouri. The Missouri team says that their battery design can hold a million times as much charge as standard batteries. The design challenge now, as previously mentioned, is to scale it down in size. But it’s not only the downsizing of the batteries that presents a major design challenge.
Nuclear batteries are an attractive proposition for many applications because the isotopes that power them can provide a consistent and useful amount of current for many years. So what’s the problem?
Most nuclear batteries use a solid semiconductor to harvest the power particles produced by the nuclear process, but the particles’ very high energies mean that the over a period of time, damage is sustained by the semiconductor.
To overcome this problem, the Missouri team employed a liquid semiconductor to capture and use the decay particles. This allowed the particles to pass without causing damage. In the long term, there’s no doubt that this highly valuable research will help overcome many of the size-to-power-related design challenges facing electronic designers.
Only the other week I was looking at the ratification of the 802.11n communications standard by the IEEE and how this standard encompasses MIMO technology. Ultimately, it will provide many design advantages for engineers working in the handset communications sector.
However, to provide those operational advantages, MIMO puts greater demands on its power source. Therefore, in order to employ MIMO, power considerations must be addressed to ensure the practical exploitation of that technology.
Consequently, pioneering power work by teams like those led by Jae Wan Kwon at the University of Missouri will surely help to overcome some of the power design challenges of the future.