Nanocar Race: Watch the World's Smallest Racing Competition Here
The race, which is meant to promote molecular machines and nanotechnology, will be livecast over the web on April 28 beginning at 10:45 am Paris time.
This week, the leading lights of the nano-chemistry world are gearing up for a molecular grand prix in the south of France.
Six teams will race tiny “nanocars” using an electron microscope at the Center for Materials Elaboration and Structural Studies (CEMES) in Toulouse. Instead of helmets and neck-breaking speeds, you can expect lab coats and up to 38 hrs of intense focus on an infinitesimally small golden track that is roughly one-thousandth the width of a human hair.
Organizer Christian Joachim came up with the idea for the nanocar race — the world’s first — in 2012 as a way to drum up public interest in molecular machines and nanotechnology. A scanning tunneling microscope (STM) can produce images at an atomic level. While most STM models have only one scanning tip, CEMES has a unique model with four, allowing four teams to race their vehicles at once. The original plan had been to eliminate two teams from the final, but that pair will participate remotely using their own one-tipped STMs.
“They are all in the final because in fact they all worked so hard for two years, that I thought it was not possible to eliminate anyone,” Joachim told Seeker.
The race will be livecast over the web on April 28 beginning at 10:45 am Paris time.
The nanocars consist of a single molecule, made up of 100 or so atoms. The track will be 100 nanometers long, held in a vacuum and kept just a couple of degrees above absolute zero.
STMs consist of a highly polished gold surface (because the metal is very non-reactive), and a tungsten tip that is so incredibly fine that its apex is a single atom. The vehicles will be placed onto the gold surface and both steered and observed by electrons fired from the tip. Every hour, participants will produce an animation of their progress and post it online.
Although the molecules are billed as “nanocars”, some bear scant resemblance to a vehicle.
“Our nanocar has two paddles, called binaphthyl, on both sides, which can move like a butterfly’s wings,” said Waka Nakanishi of the Japanese team, from the National Institute for Materials Science. Electrons fired from the STM will cause the butterfly wings to vibrate around the central chassis, propelling the vehicle across the gold surface.
The butterfly shape makes their molecule quite flexible, Nakanishi said, which could work for or against them. Her team isn’t really sure, since their molecule hasn't been tested on gold yet, only at the interface between air and water.
This uncertainty is all part of the fun — no one seems to be too certain about how their molecules will behave.
“First, bringing four different molecules on the same surface and driving them in parallel with four STM tips is a gigantic challenge,” said Rémy Pawlak of the University of Basel’s team, which will pilot a molecule dubbed the Swiss Nano Dragster. The smallest molecule of the competition, it consists of three pyridine units and one front 4-methylphenyl unit linked by single C-C bonds.
“The design is simple and expected to be robust,” Pawlak said, adding that they hoped that limiting the molecule’s size will keep friction forces to a minimum and give it a “well-defined interaction with the surface.”
To get the molecules onto the surface, they have to be deposed, or sublimated — that is, changed from a gas state to a solid state directly, bypassing the liquid state. Different molecules have different sublimation temperatures, which makes this extremely complex. Deposing a single molecule at a time makes things even more difficult. The word fiddly doesn’t even begin to describe this process.
During a Skype interview from his office in Toulouse, Gwénaël Rapenne, a chemist at the University of Toulouse-Paul Sabatier and team leader of the French team, held up a small glass flask with a trifling amount of green substance inside it.
“This is our nanocar inside, the Green Buggy,” he said. “This is maybe five milligrams, and five milligrams corresponds to millions and millions of molecules.”
The French team modeled their molecular machine on a car, but with an eye to its function after the race is over. Their design has four wheels around a rigid backbone, creating a “cargo zone” area in the middle. They hope that the Green Buggy might eventually be able to transport a separate molecule, such as a fullerene molecule, which is made entirely of carbon and shaped like a football.
“We can imagine eventually being able to deliver something like glucose, or other molecules, to somewhere else,” Rapenne said.
“We did not design it to be the fastest,” he added, as they conceived their design before the race was planned.
Once the molecules are on the track, there’s still much that could go wrong, including accidentally destroying them with voltage pulses from the STM tip, or stranding them in defects or contamination on the gold surface.
Seeing how the molecules behave under these conditions in contrast to others is one of the most exciting aspects of the race for the researchers who are involved.
“A chemist’s art is to design molecules,” Joachim said.
For one thing, he noted, they don’t really know whether wheel-type structures are actually needed at this scale to move molecular machines across a surface. His hunch is no.
The German team is also betting that wheels are unnecessary, and have instead opted for a molecule that looks like windmill blades.
“It is quite special, as we actually have four molecules kept together by hydrogen bonds, which are quite weak,” said Francesca Moresco, a senior researcher at the Technische Universität Dresden who leads the German team.
Moresco’s team believes that the weak hydrogen bonds will enable them to steer their vehicle more precisely by directing electrons at one of the “blades,” though she conceded that the bonds might in fact slow it down.
“We use electrons to go from the tip of the STM to the molecule, and these electrons excite the molecule electronically, in a way that when the molecule once again, let’s say, relaxes, it uses this energy to move,” said Moreseco. “It is more complex, of course, but that’s the basic idea.”
Other teams are using the electrical field that the STM creates between the tip and the surface.
The Austrian-American molecule is made from carbon, hydrogen, oxygen, and nitrogen. Like the French team's Green Buggy and the Ohio University team's molecule, the Ohio Bobcat Nano-Wagon, the Austrian-American molecule also looks “roughly like a car,” said pilot Grant Simpson of the University of Graz. Dubbed the Dipolar Racer, it contains a concentration of positive electric charge separated from a concentration of negative charge, which is known as a dipole.
“The tiny dipole of our molecule is able to interact with the electrical field of the tip in order to achieve lateral motion,” Simpson said.
Rapenne, the leader of the French team behind the Green Buggy, said that he and his colleagues are also working on a nano-scale motor, consisting of a unmoving stator deposed on the surface and a rotor on top of it, which could be rotated clockwise or counter-clockwise depending on where the electrons from the STM tip were aimed.
The 2016 Nobel Prize was awarded to three chemists who made pioneering advances with molecular machines in the 1980s and 1990s. They have suggested that nano machines could one day be used for diverse purposes, such as detecting cancer or as electronics that would serve as the basis for more efficient devices.
Rapenne said that although his team has no specific target applications in mind for either of these functions, it is conceivable that, if successful, his nano-technologies could be used to operate in cells or other biological settings.
But at the moment, he said, “we just want to answer some fundamental questions.”