Thanks to 3D printing, we can make circuits on the nano-scale, meaning we can make smaller electronics that could fit anywhere. The problem with this cool nanocircuitry is that it isn’t actually cool in the sense of physics – all electronics release heat. Conservation of energy states that energy can’t be created or destroyed, it just changes forms. Considering some energy is lost as it moves along a wire or some material, guess how that energy is lost? That’s right – heat. Too much, and that leads to performance loss (slows down your computer) and overheating. That’s why computers need fans and heatsinks; computers and video game consoles have lots of these, and the more powerful the computer, the more heatsinks you need. If you’re a gamer or hardcore PC (‘personal computer’, not ‘political correctness’) user with your own rig, cooling is serious business. Liquid nitrogen isn’t unheard of for PC boffins who laugh at the idea of fans – they want something that you would use to cool a scanning electron microscope.
With nanowire circuitry, it gets even more complicated because these wires are, well, small. Such is the nano-scale. Heat escapes from wires – or anything really – because of vibrations. See, all atoms vibrate unless you’re in absolute zero, according to the Third Law of Thermodynamics. These vibrations are caused by thermal energy, and can even generate more thermal energy at the cost of electric energy. This is why I brought up the extreme cooling measures, why XBox 360 and PlayStation 3 fear the Red Ring and the Yellow Light (both ‘of Death’) respectively, and why you should never, ever, ever, EVER, take your smartphone into a sauna. Seriously, it’s a sophisticated and expensive piece of scientific development, married to contemporary artistic design, and you’re taking it into an environment that’s hostile to it just so you can have something to entertain yourself when you’re supposed to be relaxing unplugged from the world, JUST WHAT ON EARTH IS THE MATTER WITH–
-sorry. Breaks my heart when I see people abuse their tech, and all the work that’s gone into getting it into their hands in the first place. But, I’m a scientist, and I’m here to inform. Keep to the mission.
Anyway, there’s a branch of scientific research (mostly in physics, but it overlaps a lot of things) that looks into phonons, which is the excitation (which is often vibration anyway) of atoms or molecules in solids and liquids. It’s called ‘phonons’ because the vibration of particles can, under the right conditions, generate sound. Anyway, in today’s Featured Article (wow, just now I get around to it?), Kargar et al. look at how phonons propagate across a nanowire. If we get a better idea on how phonons conduct heat, we can get a better idea of how to make nanowires so there’s limited energy waste, so we don’t need to tack on cooling system upon cooling system. Or risk having an exploding phone – that’s not among the reasons why phones seem to be exploding, but why add to them?
A lot of the phonon vibrations the authors are investigating are in the giga- to terahertz (GHz – THz) range, which is billions to trillions of vibrations per second. We might remember from high school physics that vibrations of light waves are proportional to energy, so it’s not really a huge stretch of the imagination to think that vibration of particles (so, sound, really) is also proportional to energy, but I don’t have the equation handy, and we would be straying from the ‘casual’ part of sci.casual.
So what did we learn, apart from don’t take your smartphones into a sauna? The authors suggest that if we get a better idea of how phonons spread through really, really thin wires, we can get a better idea of how we can build them in order to make them more efficient. Is that even feasible, though? This scientist says yes, because 3D printing allows us to do that. Sometimes, better tech means less hardware failure.
Featured Article: Kargar F, Debnath B, Kakko J-P, Säynätjoki A, Lipsanen H, Nika DL, Lake RK, Balandin AA. (2016) Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires. Nature Communications 7. DOI: 10.1038/ncomms13400
Featured image credit: Wikimedia Commons (CC-BY-SA-30, Author: Victorrocha, 2008)