On a cross between physics, chemistry, biology and what some could possibly call blasphemy, European scientists have developed a self-assembling integrated circuit, an important step towards the ultimate goal: self-assembling computers.
According to Geoff Brumfiel in
Nature, a team of European physicists has developed an integrated circuit that can build itself. Today, the building of computer chips is slowly pushed to the limit. Computer chips are made by etching patterns onto wafers made of semiconductors. The details of these patterns are no more than a few tens of nanometres. For us humans, it is nearly impossible to realize how small this is. There are 1,000 millimetres in one metre (25.4 in one inch), there are 1,000 micrometres in one millimetre and there are 1,000 nanometres in one micrometre. In other words, there are 1 billion nanometres in a metre or one million in a millimetre. Current technology is really getting to the limit, therefore other methods have to be found.
Dago de Leeuw, a researcher at Philips Research Laboratories in Eindhoven, the Netherlands, thinks that the most obvious solution is to let these circuits build themselves. We know that this is possible, since nature is chock-full of self-assembling machines: microbes, plants and animals, including humans. This is done via our genetic code that steers the entire process. In order to create truly self-assembling computers, scientists must come up with an entire new but similar system that would be able to get insulators, conductors and semiconductors to automatically link to each other. According to de Leeuw, this is still a long way off.
Nevertheless, the team has made a first step, and as usual, the first steps are the hardest ones to take. They took quinquethiophene, a long organic molecule with mobile electrons that acts like a semiconductor. They attached it to a long carbon chain, terminated by a silicon group. The silicon group acts as an anchor.
They then took a circuit board with preprinted electrodes and immersed it in a solution of these new molecules. Billions of molecules hooked on to an insulating layer between the electrodes. As a result, they formed connections through which a current could flow.
"The different molecules are like little bricks," says Edsger Smits, another researcher at Philips. "Frankly it worked much better than we expected."
They used this technique to construct a simple circuit that generates a code, based on an input voltage. The system is obviously dependent on the template of preprinted electrodes but the circuit did truly assemble itself. "We dump it in a beaker with a solution of the molecules, we take it out, we wash it, and it works," says de Leeuw.
Hagen Klauk, an electrical engineer at the Max Planck Institute for Solid State Research in Stuttgart, Germany, is a bit less excited. He says that the technique is certainly impressive, but that it still needs improvement. "Self-assembly and nanotechnology is certainly cool, but the one thing missing is higher performance," he says. The electrons aren't very mobile through the circuit and a computer constructed with this technique would be very slow indeed.
Klauk is nevertheless hopeful that the molecules can be improved upon and that the technique can be adjusted in order to eventually lead to self-assembling circuits that deliver better performances than current technologies, with thick layers of organic molecules.
De Leeuw says that, as a next step, they have to find a way to develop self-assembling electrodes. However, the breakthrough they just made could already have important uses. Because the molecule bridges are very thin, they are extremely sensitive to passing particles. The team believes that this property could be used to develop sensors for different kinds of air pollutants, such as pathogens or dangerous chemicals.
One can't help but see the parallel between this search for new computer building technologies and abiogenesis, the creation of life out of lifelessness. One of the most important properties of life is that it is self-replicating. By creating self-assembling computers, we could not only create self-replicating computer programs, a decades-old technology, but also create self-replicating machines on which to run these programs.
It is not hard to understand that this discovery can easily be seen as a next step to generating artificial life, and a better understanding of how life originated on this planet.
