The Road to Molecular Machines
Oystein Fjeldberg, Staff Writer
The 2016 Nobel Prize in Chemistry will be awarded to three scientists who have developed molecules that can be controlled in unique ways, according to the prize announcement by the Nobel Committee for Chemistry on October 5. Their efforts may lead to the advent of sophisticated molecular machines, which could be the next great technological revolution.
In the molecular world, everything is chaos. Molecules behave in unpredictable ways, as their movements are governed by randomness. Making a machine within this seemingly untamable realm might appear like an unsurmountable task, because with any functional machine the parts that make it up must be possible to control.
Before a molecular machine can be built, the chaos of the molecular world has to be overcome. Furthermore, molecules are normally held together through strong rigid bonds, which leaves little room for movement within the structure of the molecule. This is a poor starting point for making a machine, which depends on movable parts in order to work. The awardees of this year’s Nobel Prize in Chemistry are scientists who took important steps in overcoming both of these challenges.
Already in the 1950s scientists had managed to create molecules which allowed for the movement of loose parts within the molecular structure. The problem was that they were made in so small quantities and with so unreliable methods that they had no practical use. It was not until decades later that molecules like these could be made in exploitable amounts.
The first major breakthrough came in 1983, when Jean-Pierre Sauvage of the University of Strasbourg successfully intertwined two molecules rings. Each ring was free to twist and spin on its own, but was at all times locked in together with the other ring.
The rings were not connected by the kind of rigid bond that is prevalent in nearly all molecules; with this bond, each ring could move independently of the other whilst staying interlocked with the other ring. The bond that binds the molecule together is mechanic, which means that the rings are interlocked without them interacting chemically with one other; molecules with this kind of bond have subsequently been classified as catenanes. With the creation of catenanes, scientists could for the first time envision the possibility of making a molecular machine.
“It took us five years to do it,” Sauvage said of the research in an interview with Le Monde. “We kept learning from our mistakes as we went on, but it was depressing at times; there is little joy when things don’t work.”
Attempting to do something that no-one had done before meant that there was no past research for the scientists to rely on. “It is much harder to draw on a blank sheet of paper than if there already are lines,” Sauvage said.
Another important breakthrough came in 1991, when Sir James Fraser Stoddart of Northwestern University thread a molecular ring onto a molecular rod. The structure was assembled by taking advantage of a small opening in the ring that allowed it to be “clipped” onto the molecular chain (the rod). The rod had a big bulky molecule group on each end, which prevented the ring from sliding off.
Through continued research, Stoddart improved this technique to the point where he could fully control the position of the ring on the rod. The “dumbbell”-shaped molecule, which was given the name rotaxane, proved to be another important tool in the assembly of molecular machines.
By utilizing rotaxanes Stoddart went on to create simple molecular machines, such as a lift that could lift itself 0.7 nanometers above a surface, an artificial muscle that could bend a thin layer of gold, and a computer chip with 20 kB of memory (made from transistors much smaller than the ones used in computers today).
“The miracles that are happening now or are about to happen in nanotechnology have not happened overnight,” Stoddart said of the advances at a presentation at Northwestern University. “They may have for some people, but for me it’s been 40 years in the making.”
He has great faith in the technology, and believes that “it will be mind-blowing what can be done even in 10 years’ time, let alone 50.”
Bernard L. Feringa of University of Groningen, the final awardee, made another important contribution when he made the first molecular motor in 1999. Under normal circumstances a molecule will spin in random directions and never move predictably in any distinct direction. Feringa’s motor was a molecule that spun continuously in a single direction, which marked the first time that a scientist was able to control the rotation of a molecule. By 2014, Feringa had increased the spinning speed of the motor to 12 million revolutions per second.
In 2011 he utilized this technique to build a nano-car, which used four molecular groups spinning in the same direction (the “wheels”) to move the “chassis” of the molecule forward. He also used the motors to spin a glass cylinder 10,000 times the size, demonstrating their strength. The potential applications of these curiosities are numerous, according to Feringa himself.
“Think about tiny robots that the doctor in the future can inject into your blood veins and that go to search for a cancer cell, or go in to deliver drugs,” Feringa said in an interview with Elsevier Journals. “We recently developed an antibiotic that we can switch on and off; once it has been active in your body at a certain spot of an infection it will automatically switch off.”
As they all have made important contributions on their own to the field, Jean-Pierre Sauvage, Fraser Stoddart, and Bernard Feringa will share the 2016 Nobel Prize, and the monetary award of $930,000 will be split evenly between the three of them. The Prize ceremony will take place in Stockholm, Sweden on December 10.
Although there already has been a lot of talk about molecular machines’ future applications, like the prospect of nano-robots, smart materials, and molecular computers, the Nobel Prize Committee emphasized in their own press release the fact that no-one knows yet how significant of an impact molecular machines will end up having.
It should be kept in mind, according to the press release, that “in terms of development, the molecular motor is at about the same stage as the electric motor was in the 1830s, when researchers proudly displayed various spinning cranks and wheels in their laboratories without having any idea that they would lead to washing machines, fans, and food processors.”
It is hard to tell what will eventually become possible with molecular machinery, and it may revolutionize today’s technologies in unprecedented ways.
Donna Nelson, the president of the American Chemical Society, said that “this perhaps will be an area in which most of the applications will follow the award, rather than precede it. Given the attention that comes with a Nobel, perhaps this is going to come along faster than we anticipated.”
Edited by: Sara Gunter