The three Nobel Laureates made crucial contributions to a new field in chemistry: molecular machines, or nanomachines. They created synthetic molecules that perform functions that were previously the preserve of biomolecules – like changing their shape and function when energy is added.
The French chemist Jean-Pierre Sauvage came across the possibility of nanomachines while studying something else: He was working with photochemistry, a field in chemistry where researchers develop molecular complexes that can capture the energy from light and utilise it to drive chemical reactions. When Jean- Pierre Sauvage and his team in Strasbourg built a model of one of these photochemically active complexes in the early 1980s, he suddenly saw its similarity to a molecular chain: two molecules were intertwined around a central copper ion. This was a turning point for his research interests.
Next, Sauvage’s team constructed one ring-shaped and one crescent-shaped molecule that were attracted to a copper ion (see graph below). In a second step, the group ‘welded’ together the crescent-shaped molecule with a third molecule so a new ring was formed, creating the first link in a chain. The researchers could then remove the copper ion. The crux was: the single chain links have a mechanical bond, but can move freely in relation to each other within the limits of this new type of bond.
While Sauvage was using organic molecules plus a metal ion, Fraser Stoddart also created a so-called ‘topological link’ between molecules, but without using metal atoms, creating a new type of bond as well. As he explained on the day of the Nobel Prize announcement at Northwestern University where he’s a professor: “Worldwide, several thousands of new chemical compounds are generated every day. And new chemical reactions are found maybe a dozen a month. But new bonds: they are few and far between.”
Then in the early 1990s, both researcher teams started to set their creations into motion independently. Stoddart created a ring-shaped molecule that is mechanically attached to an axle. From this starting point, his team buit a ‘molecular shuttle’ where a molecule jumps from left to right when energy is added, as well as a ‘molecular elevator’ where the molecule is able to physically jump up and down. He worked with adding or subtracting electrons, chemically speaking this is called oxidation and reduction. Furthermore, his team developed molecules that can contract and expand like muscles, and switches that might be used as parts of novel computer chips. Here’s a diagram of Stoddart’s molecular elevator:
In the telephone conversation with Göran Hansson at the end of the Nobel Prize announcement, Bernard Feringa explained how he also had been studying something else when he came across the possibility of nanomachines: “The idea was to have an alternative for information storage. Suddenly we discovered that besides switchings, we could achieve movement. Then you realise you can control motion on a nanoscale.”
Already in 1999, Feringa, professor at the University of Groningen in the Netherlands, built a complicated molecule that could spin continually in the same direction. Four of these nano-motors on an axis became his famous nanocar of 2011 that can ‘drive’ across a metal surface. In this setup, the ‘fuel’ for this car comes from a scanning tunelling microscope, or STM.
Currently, several research groups around the globe are working on making these synthetic molecules more complex – they’re resembling biomolecules more and more. Nanomachines are predicted to change our lives in unimaginable ways. Mark Miodownik, a material scientist at the University College London, explained in the Guardian how the advent of nanomachines could transform the very fabric of cities: “If you want infrastructure that looks after itself – and I think we do – I’m pretty sure we’re going to be moving towards self-healing systems.” He continued: “We’ll have plastic pipes that can repair themselves or a bridge that when it gets cracked has these machines that rebuild the bridge at a microscopic scale. (…) The potential is really immense.”
On the phone with Göran Hansson, Bernard Feringa himself said: “It’s a bit early days, of course, but once you are able to control movement, all sorts of things are possible. Think about tiny little robots that the doctor would inject into your bloodstream, and that would go search for a cancer cell or deliver a drug.” He compared his work to that of the Wright brothers, who could not possibly have imagined today’s aircraft. And the Nobel Prize Committee wrote: “From energy storage, computing, medical applications to sensors: in a way, the molecular motor is at the same stage as the electric motor was in the 1830s, when scientists displayed various spinning cranks and wheels, unaware that they would lead to washing machines, fans, electric trains, etc.” The Nobel Committee concludes that this year’s laureates “have taken chemistry to a new dimension”.
But as Lars Fischer from Spektrum, the German version of Scientific American, points out, among others: there’s still a long way to go. There’s no way yet to continually fuel synthetic molecules in the bloodstream with the help of STM, and the technology to coordinate millions and billions of these molecules in smart materials still needs to be developed. Yes, it’s a new era in chemistry, but it will probably be a long era – we’re still using many electrical machines, so a long era isn’t necessarily a bad thing.
When asked about possible risks of his inventions, Feringa told the Stockholm press conference via telephone that he didn’t have any nightmares about that: “We have to think about how we can handle these things safely, but I’m not so worried about that. (…) We will have the opportunity to build in safety devices if that is needed.” You can interpret his statement as follows: It will take long to built these medical nanobots and smart materials – so this will provide enough time for the researchers to invent suitable safety strategies; this latter aspect is a huge future field of study as well.
Fraser Stoddart also stressed that his inventions took a long time: “None of us can actually forcast discoveries. It comes with working for many years, in my case 35 years, it’s not overnight, it’s a long haul.”
The topic of the 67th Lindau Nobel Laureate Meeting in June 2017 will be chemistry – we’re sincerely hoping to welcome some – or all – of the 2016 Nobel Laureates in Chemistry in Lindau!