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Papiroflexia

Folding thoughts since 1873

Archive for the 'Nano' Category

Unfolding the Universe

Tuesday, February 13th, 2007

“You have to make me another dragon!” exclaimed AH before I’d even had a chance to sit down. She was referring to the origami dragon I’d made a few weeks before, at some pub, out of a paper placemat. At some point, her husband J (who wasn’t present at The Folding) decided to find out exactly how it was done, and unfolded it all the way back to its natal square. Of course, as is typical in these cases, it was impossible to fold it back into its dragon shape once flattened, and now I was on the hook to produce a replacement.

This urge to unfold the origami, presumably to reveal its mysteries, is something I come across quite frequently. Seeing a folded paper dragon, with four legs, two wings, a tail, and a horn on top of a head at the end of a long neck, is a challenge to many. Was it really folded from a single piece of paper? No cuts? How? And a few minutes later, I’m on the books as owing another dragon.

I think it’s a fairly basic need in most intelligent people, the desire to know that as complicated as something may seem, it’s really just a permutation of objects and processes that are easy to understand. That a flat square of paper can take the form of a dragon is something that requires exploration and examination, just to make sure that the universe is operating as expected and nothing beyond the realm of an ordinary fold is transpiring.

I’m finding parallels between this and what’s going on in my nanotechnology class. We can say that all matter we encounter here on Earth is made up of protons, neutrons and electrons. These in turn are made up of a large number of esoteric and not fully-understood particles, but for our purposes let’s stop at the atomic level, just like we stop at the paper level and not get into the plant fibers and their bonding structure. Our friends the atomic particles are limited in variety, yet they combine to make a seemingly infinite realm of possible materials. Air, water, copper sulfate, sushi — these are all built from protons, neutrons and electrons, yet are as different from each other as you could imagine.

Of course, chemistry and physics have gone a long way towards explaining how these partners dance around each other and form bonds and relationships that give us the characteristics we observe, but the explanation is nowhere near complete. What’s more, new exceptions to the long-accepted psychology of atoms and molecules are being found, as I’m discovering in my nanotechnology class. Imagine two atoms, anthropomorphized into your hippie girlfriend and your nutty über-Republican uncle. Under normal circumstances, they wouldn’t bond. In fact, you could say those two will never bond, and most likely, everyone would say you are right. But take them to a German pub and watch as their mutual interest in fine lagers unfolds, and the next thing you know one of them is saying “we should do this again sometimes.” Things like this happen all the time in nanotechnology — things like gold bonding to DNA.

In a lot of ways, part of nanotechnology is trying to unfold the universe of matter into basic squares of paper, which it can then re-fold and assemble at will. Another part is trying to come up with the tools to actually make these folds — it’s not enough to dream up fantastic molecular objects with esoteric properties if you’re not able to manufacture them in the trillions. Obviously, our fingers aren’t small enough to make those folds, so we must depend on surrogate tools to manipulate these individual atoms and molecules. A lot of current nanotechnological processes are the equivalent of wadding up a billion pieces of paper and sorting through them to find the ones that are most dragon-like.

But there’s no doubt that technology and understanding are progressing at a frenetic pace in this field, and someday, maybe within our lifetime, we’ll be able to fold up whatever we need out of little molecular squares and an instruction book.

Nanostuff

Thursday, January 25th, 2007

Tonight I have class, so I’m thinking about nanotechnology a lot, probably because I have to read a buttload for each class. Additionally, I’m getting weird informational spikes on things like DNA (Crick was trippin’), mitochondrial cancer cures that won’t be funded, and such. Nanotechnology as a science is on the path of understanding more and more complex interactions between atoms and molecules, while biology is intent on breaking down to the fundamentals of how life works. I get the feeling the two are going to meet somewhere in the middle, and then we’ll have to come up with whole new definitions for “life,” “consciousness,” “free will,” and other such abstractions we take for granted now.

Scanning and Tunneling

Tuesday, January 23rd, 2007

As part of my Nanotechnology course, I went to a demonstration of nano-scale microscopy at a lab here in school last night. Led by the very capable Dr. Z., it provided some background and demonstrations of Scanning Tunneling and Atomic Force microscopy (respectively STM and AFM).

Traditional optical microscopy goes down to the micron (meaning a millionth of a meter) level of resolution. If you want to be able to see things like atomic structures of materials, you have to go a thousand times smaller, to the nano (billionth) meter. A hydrogen atom is about a tenth of a nanometer in diameter, and larger molecules can be hundreds of nanometers.

However, it’s not possible to see things smaller than a micron with visible light, due to limitations in quantum physics and such. You can shorten the wavelength into the ultraviolet and get a bit more resolution. Theoretically, if you reduced the wavelength to the x-ray level, you could use photons to measure even finer scales, but there’s the practical problem of constructing an x-ray lens to focus your image.

So — we use electrons (in the case of STM) and a way of measuring nanoscopic deflections (for AFM) in order to get an idea of what things “look” like at that level. Dr. Z. spent about an hour going over the instruments’ history and operating principles. It’s interesting to think that this scientific tool is fairly new — 20 or so years old. Already the advances in the technology are evident, since the original dumpster-sized contraptions have shrunk into something about the size and shape of a sugar bowl on a cheese cutting board.

An STM gets an idea of what an atomic surface looks like by moving a needle that’s impossibly close to the surface and measuring minute fluctuations of current between the needle and the surface. A significant limitation is that whatever you’re scanning has to be electrically conductive. And flat. Like atomic-scale flat, or your needle’s going to ‘crash’ — actually make contact with the surface. Although the needle contains uncountable atoms, in theory (if prepared properly), it has a single atom at its tip.

Perhaps the coolest thing is that the instrument relies on a quantum effect — electron tunneling — for its measurements. The microscope itself, branded Nanosurf, looked like a squat golden cylinder resting on a square slab of granite. Apparently, a lot of the technology behind this is the result of some “Mars 2001 program,” obviously long-scrapped.

STMYou place your sample on a little magnetic cap that goes on a cylinder, place the cylinder into the notch cut out for it, then move it (using tweezers) to about a millimeter of the needle. That’s the end of the romance between your meaty human hands and this delicate apparatus. From this point forth, you control everything via software, computer and interface boxes.

We imaged some graphite. Getting a good picture in nanoscale microscopy is rife with intuition, prior experience and almighty quantum luck. In this case, individual atoms weren’t clear, but we could see a regular “step” pattern where the layers of graphite had been torn at an angle.

AFMThe AFM works by dragging a tiny bar with a needle on across the surface of your sample. A mirror on the other side of the bar provides a target for a laser. As the bar (aka cantilever) deflects, the laser’s reflection results in a magnification of movement that is measured.

Operation of the AFM is similar — get your needle within a millimeter, then let the computer take over. We imaged a semiconductor chip partially before the lab was over and it was time to go.

It’s interesting to think that we can build machines that work at these terrifically small scales, and that they are affordable enough for your average university to stick in a lab with a batch of students to operate. When you add in how much these tools have advanced in the last twenty years, then scale that to the difference between, say, early telescopes and today’s radio arrays, it’s a bit spooky. What are we going to see down there in another 20 years?