Carbon nanotubes molecule structure, atoms in wrapped hexagonal lattice isolated on white background, 3d illustrationAnd so, here comes the end of June. I’ve learned a lot about nanotech this month, and at the same time, very little. Here the general gist:
Nanotechnology is a very tricky word, and because it’s still in its infancy, there doesn’t exist a crystallized definition for it, except for the concept that it operates on the nanometer scale. A single nanometer is 1×10⁻⁹ meters. I’m sure you can find resources online giving you a frame of reference, but basically, it’s really really small.
Fundamentally, a nanotech is essentially the art of making things smaller. This sounds pretty obvious, but at the small scale, the dynamics get pretty different. For one, the forces at play at the nanoscale experience a fundamental shift. Gravity is essentially negligible at this scale, as nanometer-sized objects tend to massless. Intra-molecular forces, such as hydrogen bonds and van der Waals forces, become much more important. With gravity no longer being a constraint, the concept of up and down become less of a constraint. If you think about how many buildings and structures are limited by gravity, such as bridges, skyscrapers, planes, etc., the switch in how forces interplay lead to some interesting conclusions.
At the small scale, surface areas also become much more important. The surface area to volume law says that as surface area increases quadratically, volume increases cubically. At really small sizes, objects have high relative surface areas, and low relative volumes. This means that chemical reactions experience much different dynamics. A huge limiting factors for catalysts is its surface area, as only a limited amount of substrates can take up the surface area at a time. This is why at smaller sizes, chemical reactions can happen much faster.
While there are quantum effects that happen at the nano-scale, a lot of the laws of classical mechanics still apply. To say that the laws of physics experience a total rewrite isn’t particularly correct. What’s really happening is that you’re tuning one variable (aka size), to the extreme, and taking advantage of the results of that
Let’s talk about nanotechnology’s current poster boy, the carbon nanotube. The carbon nanotube is essentially a flat sheet of hexagonal carbons rolled into a tube. The really interesting thing about this material, is a bunch of properties that, when put together, seem kind of magical:
Incredibly high tensile strength
Imagine a piece of string supporting a 100lb weight from a ceiling. If the string was made of twine, it would probably break. If the string was made of fishing wire, it would probably hold. Generally, the greater tensile strength a material has, the more weight it would be able to support. Carbon nanotubes have around 100 greater tensile strength than steel. This is because the network of carbon-carbon bonds within nanotubes support each other. When trying to pull a nanotube into two pieces, you are not trying to break the nanotube at a single cut across the nanotube. Instead, you’re fighting against every bond in the nanotube, and this is significantly harder.
High electrical conductivity
Metals conduct electricity because delocalised electrons, and when a voltage is applied to metals, electrons have the freedom to move and therefore, conduct energy. Carbon nanotubes also have the ability to conduct electricity due to delocalized electrons. In fact, they actually conduct electricity better. Electrons only propagate along the axis of the nanotube, which is a much smaller area to propagate. This results in much faster conductivity. Imagine a hose that’s spraying water. Now, imagine taking your thumb, and covering half the tip of the hose. What you’ll see here is that the water will eject out faster. A similar concept applies at the nanoscale, where if the axis of travel is smaller, the electrons will move faster.
High thermal conductivity
Electrons are carriers of heat because of their vibrational kinetic energy. Metals are good heat conductors because of delocalized electrons that can carry heat around. Carbon nanotubes are even better heat conductors because their delocalized electrons travel faster. Similar to the explanation above, nanotubes conduct heat well, because their electrons travel faster.
All in all, most nanotechnology articles and resources I’ve looked at revolved around carbon nanotubes, because of its very interesting properties. I’m looking forward to what the field has to offer in the future.
Something I’ve learned about myself is that I tend to think much better about concepts in relation to how they’re applied, rather than abstractly. In other words, it’s harder for me to understand equations without picturing a scenario that equation would be applied to. On that note, I’m considering writing articles about the application of nanotech to emerging technologies. One of my favorite pop-sci books out there right now is Soonish, a book about 10 potentially-huge emerging technologies written by the creator of SMBC-comics. It might be an interesting exercise to write about how nanotech could potentially be applied to these emerging technologies that I might do in the future.