Features An illustration imagines a head-to-head meeting of the six nanocar competitors from around the world (left to right): the Windmill from Germany, the Green Buggy from France, the Dipolar Racer from the U.S. and Austria, the Nano Dragster from Switzerland, the Bobcat Nano-wagon from the U.S., and NIMS-MANA Car from Japan. MOLECULAR MACHINES On your ever-so-tiny mark intimately probe the electrical properties of explains. Or STM tips could crash into the molecules, he predicts. surface. Or maybe a car just isn’t optimized The rules of the race are fairly straight- The CNRS instrument will enable four for the STM driving it. There are a lot of un- World’s first nanocar race forward. Each team will drive its car along a separate teams to simultaneously move and knowns, he says. 100-nm-long, S-shaped racetrack made from manipulate molecules in a manner that’s Still, he’s happy to see the excitement gold inside an STM. The teams will propel never been attempted before. and interest around nanomachinery. Tour crowns champion their vehicles using an STM tip, a narrow Remember, though, there are six teams. has been working on nanocars for nearly 20 tungsten rod sharpened to an atomic point. All of them will be present in Toulouse, but years and the work was slow going early on, C&EN follows the action on and off the track the broken, motionless car. It raises a host Mechanically pushing the cars with the Ohio team and a team of Austrians and but that’s changing. “Molecular-scale con- of questions he and his team could choose the tip is not allowed during the race, but Americans will remotely control their cars. trol, on a surface, is now taking off in a big to answer for the first time. For example, teams can nudge their cars to the starting Thus, only four nanocars will physically be way,” he says. MATT DAVENPORT , C&EN WASHINGTON why isn’t it moving? And for the four- line. Once the race starts, each team will in Toulouse. Sander Otte of the Delft University of t’s hard to understand why Eric Masson’s excited about a wheeled cars that do move, do the wheels position an STM tip near its car and fuel skid or roll along the surface? (The team has the molecular vehicles with electrons and picture of his car with a missing wheel. The fact that the car in started looking into that question, and early electrical energy, which drivers control by “Having an element of competition the sepia micrograph on his computer screen looks more like evidence suggests rolling, Masson says.) modulating the tip’s voltage. The first team a toasted marshmallow than a Maserati doesn’t help, either. Even seeing the lost cucurbituril wheel to complete the course wins. always inspires people to come up with I lying on its side was exciting for the Ohio The basic guidelines disguise the myriad But Masson, a supramolecular chemist at Ohio University, patiently team. Nobody had ever imaged that with complexities of coordinating a molecu- creative solutions and try out new ideas.” explains that the lumpy, cream-colored rectangle he’s pointing to in an STM before. Researchers are seeing lar-scale race, not to mention the multitude the scanning tunneling microscope (STM) image is an assembly of and manipulating molecules on surfaces of opportunities for things to go wrong. “I Sander Otte , Delft University of Technology like never before, which could open new feel like we’re launching a rocket,” says race atoms that scientists can drive across a surface. It is a nanocar. doors in surface chemistry and solid-state organizer Christian Joachim, a researcher The remaining two will be controlled by Technology is a master at manipulating There are several similar rectangles in race, staring at the team’s immobile technology. in the Nanosciences Group at CNRS. “We pilots in Toulouse linking up to their own atoms with STMs. Although he’s not part this STM image. All of them, except for one, three-wheeler. The naïve nanocar observer Masson’s perspective is best captured in have to make sure all the little technical de- STMs in Ohio and Austria, Ohio’s Hla says. of the race, he is a fan. “It is fantastic that feature four discernible lumps, one at each wonders what happens if this hobbled mol- the three possible outcomes he sees for the tails are accounted for.” That means Ohio’s drivers will be mov- events like these are being organized,” he corner. These lumps are nanocar wheels ecule takes to the track against more ambu- race. The first is that the Ohio team wins. Along with his collaborator, Gwénaël ing an STM tip and their car with nanoscop- comments. NIVERSITY/UNIVERSITY OF BASEL/ made of large, ring-shaped cucurbituril latory competition. The thought generates The second outcome is the team loses. The HUTTERSTOCK Rapenne, Joachim first publicly proposed ic precision from across an ocean. If that But he also thinks it may be a little gener- molecules. feelings closer to anxiety than excitement. third is the team loses because its molecu- the idea of a nanocar competition back in impresses Hla, it doesn’t show. “That’s to- ous to label all of the race’s entrants as true But the car Masson’s pointing at has only But Masson has a different, more com- lar car does something totally unexpected 2013 ( ACS Nano, DOI: 10.1021/nn3058246 ). day’s technology,” he says, matter-of-factly. nanocars, especially compared with the three lumps. Resting nearby is a bright cir- plete view of his nanocars and the race as a during the race. “That outcome is the most After that, it took about three years to put Still, all this technology has steered the work of newly minted Nobel Laureate Ben cle—a cucurbituril wheel lying on its side. whole. From a simple standpoint, the race exciting one to me,” Masson says. together a budget, find sponsors, and select nanocar race into uncharted territory, and L. Feringa. The car missing its wheel refuses to is a friendly international competition that There is, however, one more feature in the six racing crews. as anyone who has played Oregon Trail can Feringa and his team developed molecu- move, Masson has learned from his col- will showcase new STM technology at the the image on Masson’s screen that suggests Rapenne is actually leading one of those attest, pioneering is fraught with broken lar machines with moving parts energized league and STM sage, Saw Wai Hla . Perplex- French National Center for Scientific Re- he’d also be happy with the first possibility. teams, the Toulouse Nanomobile Club. wheels and axles. by light or electric current, for example. The ingly, this is exciting news. search (CNRS) in Toulouse. Between the lumpy rectangles are a handful The team synthesized a C184 H116 nanocar “Anything can happen,” says James M. motion of these parts translates to motion Masson, Hla, and their coworkers make But the bigger picture is that the race is of horizontal beige lines. The team thinks dubbed the Green Buggy. Tour, a leader of the American-Austrian of the entire molecule, like a car carried by up one of six international teams preparing giving molecular machinists a platform to these are blurs in the image created by The Green Buggy will be one of four Nanoprix Team and a synthetic organic its rotating wheels powered by the vehicle’s for the first-ever nanocar race on April 28 in show where the field is headed. And, for the four-wheeled nanocars zipping by the STM nanovehicles racing inside a state-of-the chemist at Rice University. Tour also led engine. Molecular machining has allowed France. Because Ohio University is within researchers involved, synthesizing and rac- probe as it “photographs” the surface. The art, four-tip STM at CNRS. Although mul- the first team to unveil a single-molecule nanocars to shift from neutral to drive. driving distance of C&EN headquarters— ing the nanocars has presented rich oppor- molecular cars are literally streaking across titip STMs are not new, this one can achieve car , as C&EN reported back in 2005 (Oct. Based on the information available to using a macroscopic car, of course—we tunities to push the limits of new technolo- the screen. picometer resolution with each of its tips, 24, page 13). C&EN on the race’s website, the Green Bug- were able to visit the team. gy and learn new science, Masson says. “Apparently these things fly,” Masson and that is totally new, Joachim says. Be- Cars could get stuck in single-atom im- gy may come the closest to that advanced RICE UNIVERSITY/G. RAPENNE/P. ABEILHOU/CEMES-CNRS/S So here we are, two weeks before the That helps explain why he’s excited about says, smiling. CREDIT: YANG H. KU/C&EN/TU DRESDEN/MANA-NIMS/OHIOyond U driving nanocars, this will help more perfections along the gold-paved track, he standard. Other cars in the race are more like 16 C&EN | CEN.ACS.ORG | MAY 8, 2017 MAY 8, 2017 | CEN.ACS.ORG | C&EN 17 passive wagons that can be towed around windmill’s wheel made up of four acetylbi- she says. “STM people don’t tend to look at the surface using an STM tip’s electric field. phenyl blades. them.” Teaming up with STM scientists to “Still, we shouldn’t be too critical,” Otte The outer edge of each blade provides a take on the challenge of imaging and driv- concludes, adding that he hopes there are steering point to control the molecule with ing the molecule has been one of the most more nanoraces in the future.