A farm boy, who never had electricity at home until the age of 17, went on to create a whole field of chemistry that won this year’s Nobel Prize. That boy, Fraser Stoddart of Northwestern University, shares the prize with two other scientists, Ben Feringa of the University of Groningen and Jean-Pierre Sauvage of the University of Strasbourg, which was given “for the design and synthesis of molecular machines.”
Stoddart’s inspiration came from nature. All life is powered by tiny biological machines that nature has had billions of years to perfect. The most fundamental processes of life, such as translating genetic code to make proteins or ensuring that cellular waste is recycled, require the use of molecular machines, which are 10,000 times smaller than a human hair, and function only on chemical energy.
Stoddart wanted to use chemistry to make similar-sized machines that would do our bidding. Like traditional machines, these would need parts, motors and a source of energy, but doing so on a molecular level is far more complicated. “The entire regime of motion in the molecular world is completely different to in the macroscopic world, and so what people call nanocars have nothing at all to do with the physics of a car,” physicist Dean Astumian at the University of Maine, told Chemistry World. “It’s like when you look up in the night sky and see a constellation that looks like a bear: We wouldn’t think that the biology of a bear is useful for understanding how the stars in that constellation move relative to one another.”
Sauvage made a breakthrough in 1983 when he was able to create two molecular rings that were interlocked. Then, in 1991, Stoddard made another breakthrough, where he could trap a molecular ring on a thread-like structure. Although chemical bonds created these molecular rings, they were were bound to another ring or a string through mechanical means. Those two structures gave them parts for the machines they wanted to build.
Next, they looked for an energy source. Both Sauvage and Stoddart modified the chemical structures of their rings and string to respond to electro-chemical energy. This involved addition of a certain chemical (an oxidation agent, to be specific) which added more electrons to the system. The additional charge caused the components on the ring or the string to create an imbalance, which the attached ring responded to by creating motion on a molecular scale. And vice versa.
It felt like Sauvage and Stoddart had built a molecular machine. They used their parts to create molecular structures that imitated the movement of a muscle and even that of an elevator. Through the use of a chemical switch, each could be made to change state and perform a mechanical action.
But these machines created a new challenge. Once you moved it from one state to another, it wasn’t easy to reverse the process quickly. So though they had motion, it wasn’t a motor. In 1999, that problem was solved by Feringa, who created a whole new set of molecular parts.
Feringa’s motor could respond to light and heat. With each switch of energy source, it would change state and create reversible motion. In 2011, he used four such motors and attached them to a molecular chassis to create a four-wheeled molecular car (pdf).
“What would be the utility of such machines?” Richard Feynman, a Nobel Prize-winning physicist who was among the first few scientists to start talking about molecular machines, said in 1959. “Who knows? I cannot see exactly what would happen, but I can hardly doubt that when we have some control over the arrangement of things on a molecular scale we will get an enormously greater range of possible properties that substances can have, and of the different things we can do.”
Things haven’t changed much despite the Nobel Prize. “I feel a little bit like the Wright brothers, who were flying 100 years ago for the first time. But people asked: ‘Why do we need a flying machine?'” Feringa said at the press conference after winning the prize. “[With this technology] we will be able to build materials that will change, adapt, or even store energy. There is endless opportunity.”
Together, these researchers have given scientists the tools to create molecular machines. And many have embraced them. On Oct. 14, researchers will conduct the first nanocar race in France. Though it took a while, the nanotechnology future that was dreamed up by science-fiction writers and physicists is finally within reach.