Imagine trying to read braille printed on wet tissue paper. That’s what it’s been like trying to take a picture of a molecule. Advanced electron microscopes can get amazing resolution, fine enough to see inside an atom, but molecular bonds usually aren’t strong enough to hold up to their scrutiny. Luckily, a team of researchers at IBM has produced the first Atomic Force Microscope (AFM) with a carbon monoxide tip. Using this new device, they’ve produced the first real images of a molecule. Check out the pics of the pentacene molecule, they’re one of a kind.
Being able to examine a molecule without it falling apart is a first step into understanding how to manipulate those molecules with precision. Pentacene has uses as an organic semiconductor. IBM has had success with microscopy in the past, and thinks its research will pave the way for designing and building electronic devices at the atomic level. One day, entire computers and even everyday objects could be manufactured from the atom up, allowing for incredible breakthroughs in processing power and efficiency.
Traditional microscopes like the one you had in middle school science class use visible light to illuminate a sample. Electron microscopes,which have been around since the 30s, use high powered electrons to image objects in a similar way. AFMs, however, work like fingers reading braille. They use a microscopic tip to gently run over the surface of a sample and then measure how the tip fluctuates. In this way, they build a “force-map” or textured view of what the tip passes over.
AFMs have been around since 1986, but they haven’t been able to image a molecule. Electrostatic and Van der Waals forces cause molecules and AFM tips to interact, ether destroying the sample or disrupting the readings. IBM overcame this problem by attaching a single carbon monoxide (CO) molecule to their AFM tip. Thanks to quantum mechanics, the CO and pentacene molecules have their electrons set up in a way that helps cancel out electrostatic and Van der Waals forces. In other words, the tip can pass over the sample without messing it up. The result is the first image of its kind.
Like all new microscopy techniques, the modified AFM has its set backs. First, like the electron microscope or traditional AFM, the IBM setup can’t be done in the open air. You need a very high level vacuum, absurdly low temperatures (5 Kelvin), and a lot of time – more than 20 hours for a scan. The tip also has to be within 0.5 nanometers of the sample. But the most fundamental problem is that the carbon monoxide trick won’t work for every sample type. The quantum mechanics principles that keep the tip and sample from interacting wouldn’t help for say, a strand of DNA. Of course, there are a bunch of different tips you could use, so there may be a tip for every sample you could want to examine.
As cool as it is to see a molecule up close and personal, you can bet IBM has bigger plans. Quantum computing, which is seeming less and less like science fiction everyday, will require building structures at the molecular level. With the modified AFM, we’ll get a better understanding of what’s happening at that level and how best to create computers at a nano-sized scale. That’s going to translate into better efficiency and processing speeds that make a modern computer chip look like an abacus.
Of course, even with the best views of the microscopic world quantum computing is years away from beginning. For now, we’ll have to be happy with having a better view of a pentacene molecule. Hopefully, IBM will adapt their technique to see many different nano-sized structures. It may not happen today, but work like this will help us build the tiny, magnificent world of the future.
