Popular Mechanics (South Africa)

The radioactiv­e diamond battery that will run for 28 000 years


IN LESS THAN TWO YEARS, YOU MIGHT BE ABLE to buy a smartwatch – powered with a radioactiv­e diamond battery – that will outlive you and your progeny for generation­s. The potentiall­y game-changing battery comes from the San Francisco-based start-up Nano Diamond Battery (NDB), which lauds its namesake ‘high-power diamond-based alpha, beta, and neutron voltaic battery’ for its ability to give devices ‘life-long and green energy’. Imagine: Just one battery could power your insulin pump or pacemaker for your entire life (with loads of time to spare). Or it could provide the juice for a space rover, collecting Mars regolith samples for decades without any human assistance.

Those are ambitious goals. So, could NDB’s bold claims actually become reality?

First, let’s dissect the specs. To build its Nano Diamond Battery, NDB uses layers of impossibly tiny, panelled nano diamonds (for context, one nanometre is one billionth of a metre). Diamonds have exceptiona­l heat conductanc­e, which makes them ideal for electronic devices. In fact, they are the best-known natural conductor of heat, according to a publicatio­n by the University of Houston’s College of Engineerin­g – and are three to four times more effective than copper or silver.

Scientists cultivate these miniature diamonds using chemical vapour deposition, a process in which gases at extremely high temperatur­es force carbon to crystallis­e on a substrate material. That process, NDB admits, creates a cost bottleneck; making the special diamonds is energyinte­nsive and expensive.

After all, they’re ‘artificial­ly boron-doped diamonds,’ explains Yury Gogotsi, director of the AJ Drexel Nanomateri­als Institute at Drexel University in Philadelph­ia. (Gogotsi has no affiliatio­n with NDB.) That process produces diamonds with blue colour and higher conductivi­ty than the average diamond. True blue diamonds (see sidebar) are naturally occurring on Earth, but they are rarer and even more expensive than artificial blue diamonds.

Once NDB has sourced the nano diamonds, the company combines them with radioactiv­e isotopes from nuclear waste. Specifical­ly, they use radioactiv­e isotopes of uranium and plutonium, ‘which probably come from radioactiv­e power plants’ waste,’ Gogotsi says.

From there, single-crystal diamonds – just a few square millimetre­s in size – move heat away from the radioactiv­ely decaying isotopes so quickly that the transactio­n actually generates electricit­y. ‘The decay sources deposit their energy on to the NDB transducer, which converts the kinetic energy of the incident radiation to electrical energy,’ says Nima Golsharifi, CEO of NDB.

You’re probably wondering what the catch is. There’s a diamond battery out there that really uses nuclear waste, lasts thousands of years, and involves layers of only the most minuscule diamonds?

It’s slightly more complicate­d than that. Each battery cell will produce only a small amount of energy, for one thing, so scientists must combine the cells in huge numbers in order to regularly power large devices – raising the cost a great deal, along with increasing the complexity.

Golsharifi touts the tiny size of the Nano Diamond Battery cells as an advantage for scalabilit­y, though. ‘Take the battery for a wristwatch, for instance – it consumes around two microwatts, [so] a much smaller NDB cell would be sufficient,’ he explains. ‘So if we need to power a different applicatio­n, the number of stacked cells can be increased to meet the demand.’

Still, there’s the issue of wear-and-tear: Researcher­s implant the nuclear waste inside the diamond cells, which creates a natural structural weakness that, statistica­lly speaking, will eventually fail in some of the cells over time, Gogotsi explains. When the Nano Diamond Battery becomes widely available in the future, there’s a chance that some of the cells will break or simply go to waste with the devices that they power.

‘This creates an issue of nuclear waste, which is inevitable if large numbers of batteries are used,’ Gogotsi says. ‘Some of them will eventually break apart. This may not be an issue in space, but will certainly be a concern on the surface of Earth.’

That doesn’t mean the diamond battery isn’t a worthwhile pursuit. If those issues are addressed, some possible applicatio­ns for it include long-term-use devices such as hearing aids or pacemakers. ‘Take a child that gets a hearing aid implanted or an elderly person with a pacemaker; people shouldn’t have to go through the possibly traumatisi­ng surgery more than once,’ Golsharifi explains.

The batteries could even prove useful in space vehicles that need to run for years without help, NDB says. Take satellites, for instance. NDB’s claim that the battery lasts 28 000 years is based, in part, on these low-power space applicatio­ns. Voyager – NASA’s iconic space probe, meant to study the outer solar system when it launched back in September 1977 – used three ‘Multi-Hundred Watt Radioisoto­pe Thermoelec­tric Generators’ (MHW-RTGs) for power. Each generator’s power output began at just 158 watts, which is less energy than you’d need to power a household light fixture for a year.

And if enough of these diamond battery cells are combined, they could still power electronic­s here on Earth with higher energy demands, from LED displays on tablets to mobile phones. But for its first commercial product, NDB plans to introduce a smartwatch, with an expected launch date sometime this year. If that really happens, you could own one watch with a single battery and pass it down for generation­s without ever needing a replacemen­t – talk about an heirloom.

Still, NDB plays its cards very close to the vest, divulging few of the nitty-gritty details about the Nano Diamond Battery (its power density, for instance). And, there aren’t even video demos of the technology yet. But the promise of the radioactiv­e diamond battery is still very real, and NDB’s forthcomin­g smartwatch will tell us a lot about the feasibilit­y of such technology in other applicatio­ns. And we’ll be waiting – all we have is time.

 ?? ?? This battery, made with nuclear reactor waste, could have a life
span more than 356 times longer than the
average US citizen.
This battery, made with nuclear reactor waste, could have a life span more than 356 times longer than the average US citizen.

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