The newest electric vehicle to roll out cannnot be plugged in, but it does have one impressive credential: It's the smallest in the world.
Unlike nanocars of the past that were aided by scanning microscopes, light, or heated surfaces, this molecular vehicle uses electrons to move forward.
"This is the first example where you really have a motor function," said Ben Feringa, an organic chemistry professor at the University of Groningen in the Netherlands who led the nano-vehicle's creation. "You can put in energy so you have a propulsion mechanism like in a real motor in a car."
Feringa developed the molecule with a team that included Karl-Heinz Ernst, a professor at the Swiss Federal Laboratories for Materials Science and Technology, as well as Syuzanna Harutyunyan, synthetic organic chemistry assistant professor at the University of Groningen, and Nathalie Katsonis, assistant professor of biomolecular nanotechnology at the University of Twente in the Netherlands. Their nanocar is described in the November 10 issue of the journal Nature.
Previously, Feringa had worked on designing molecular motors that function like artificial windmills. To create the new nanocar, his team attached four of these motors to a synthetic molecule. The motors act as pedal wheels that, when excited electrically, push the whole system over a copper surface. Electrons firing at the tiny car change the rotor shapes, moving them along a fraction of a nanometer. The motors are controlled individually, giving them directionality similar to steering in a macro-scale car.
Feringa and his team worked at low temperatures in a vacuum so that the molecules would stay still until activated, similar to putting on the parking brake so a real car doesn't accidentally roll downhill.
"Control of motion in the nano world is very difficult, and the motion is very different from what happens in the macro world," Feringa said. Gravity and weight don't keep a molecular vehicle grounded the way they would a human-sized car. "There's a big incentive to develop motors that ultimately can provide the energy to do all kinds of functions at the nanoscale."
While he called his advancement "very small," Feringa said that it's a crucial step in creating real, advanced nano machines. Eventually, he would like to be able to take larger steps, improving the controls, getting the molecular vehicle to work at room temperature, and move on a longer trajectory.
Paul Weiss is a professor of chemistry and biochemistry at UCLA and director of the California NanoSystems Institute. His commentary on Feringa's development appears in the current issue of Nature.
"There is some really neat complexity in what Feringa did," Weiss said. Scientists are trying to gain the kind of efficiency found in nature, converting one kind of energy into mechanical motion, he added. "We don't know where that might take us, but we do know this is a proof of principal because that's how natural muscles work."
James Tour is best known for designing a "nanocar" molecule in 2005 that, while lacking a motor, could move along a metal surface due to thermal diffusion. The Rice University chemistry professor praised the new molecule as a fundamental step in the quest to construct machines that can currently only be done biologically by enzymes.
"One can envision the capture of small molecules for the piece-by-piece construction of small devices such as electronic memories," Tour said.
Fraser Stoddart is a chemistry professor at Northwestern University known for developing structures for nanoelectric devices. He said images of the molecular electric vehicle brought back memories of riding bumper cars as a kid in Edinburgh. "They were obviously powered by little electrical motors."
Stoddart said Feringa's vehicle takes up the challenge of making machines that actually work on surfaces instead of paddling around in solution. "He knows how to bring many, many things together and make them work," he added. "It kind of reminds you of how the Wright Brothers got airplanes up in the air."