Researchers at MIT have developed photonic crystals that, in as little as two years, could enable the use of hydrocarbon reactors in portable electronic devices, and nuclear power sources everywhere else.
Photonic crystals are optical nanostructures that are tuned to specific wavelengths of light. If you understand how semiconductors affect the motion of electrons (i.e. the bandgap only allows electrons with a certain energy level to pass through), photonic crystals are the optical equivalent. In this case, MIT has created infrared-absorbing photonic crystals using metals such as tungsten and titanium. Because of their metallic roots, these photonic crystals can operate at temperatures up to 1200C (2192F).
You can probably see where this is going. Basically, every object that is warmer than absolute zero emits electromagnetic radiation — and the hotter it gets, the higher the frequency of that radiation. Once an object becomes red or white hot, some 99% of the radiation produced is infrared. MIT’s photonic crystals are perfectly tuned to absorb infrared radiation, and they can survive high temperatures. This captured energy can then be converted into electricity.
As far as suitable heat sources go, they’re a dime a dozen. As it stands, many of NASA’s deep space missions — Pioneer, Viking, Cassini-Huygens, the Curiosity Mars rover — use radioisotope thermal generators, which generate heat from the decay of radioactive material (usually plutonium, pictured right). Currently, a thermocouple is used to create electricity from the heat, but thermocouples are incredibly inefficient (they max out at around 10%). These photonic crystals would be more efficient (and MIT is already talking to NASA about it).
Looking towards the future, MIT’s photonic crystals could offer an alternative to photovoltaic panels or fuel cells. Any source of heat could be turned into electricity, without the need for turbines or any other moving parts. According to MIT researcher Ivan Celanovic, for a given weight and size, a microreactor that burns butane and uses photonic crystals could last 10 times longer than existing battery technology.
If you’re not comfortable with having a reactor in your pocket, though, the photonic crystals could be used to simply capture waste heat, much like the University of Minnesota multiferroic alloy or German magnetic RAM that we covered last year.
The best bit, though, is that MIT is confident that this technology could be brought to market in as little as two years. Photonic crystals are actually quite mature tech; the actual meat of this discovery is that they’ve found a way to cheaply mass-produce rugged crystals that can operate at high temperatures. This technology is coming.