Self-assembly could simplify nanotech construction

日期:2019-03-01 03:13:04 作者:韩菱咳 阅读:

By Tom Simonite (Image: APS/Silas Alben ) “Molecular origami” could become the latest nanotech construction technique, thanks to the first detailed study of how sheets fold. The study, which was done at Harvard University, Cambridge, Massachusetts, US, was inspired by experiments carried out in 2005, in which small flat surfaces were transformed into 3D structures such as spheres simply by shaking them at random. The shapes were fitted with oppositely charged magnets, which became stuck together, pulling the surfaces into shape. The hope is that a similar process may be possible on the molecular level, using surfaces such as graphene (carbon “chicken wire”) with dangling bonds at the edges to hold the 3D shape together. This self-assembly process might yield simpler ways to make the microscopic components required by the electronics and computing industries. But until now no one has tried to understand the process behind the phenomenon. The most advanced self-assembly research has focused on how individual particles self-assemble into sheets like lego bricks. But folding sheets could have more potential. “The previous experiments were more or less trial and error,” says Silas Alben, a mathematician at Harvard and one of the authors of the study, “they just tried to think up what would work.” Alben and colleague Michael Brenner are working towards a slicker way of doing it. “We want a way to predict what kind of shapes a given flat sheet will produce,” says Alben. The two mathematicians simulated the 2005 experiments on computer using networks of virtual springs to represent differently shaped sheets. When these were shaken, the flexing of the sheets brought certain points on the edges together, allowing some shapes to form but not others. The simulations show that these changes in shape are caused by sudden buckling rather than gradual bending. “It is like putting too much pressure on a beam,” says Alben. “Eventually it will break.” Alben and Brenner also worked on what it is about a sheet that makes it likely to buckle. For example, thicker sheets are more resilient to buckling, while sheets with curved edges focus stress in a way that makes buckling more likely. “This formula should allow us to design a sheet shape and predict which parts will buckle,” says Alben. “That should at least give an idea of the number of possible shapes for a particular sheet.” It is not yet possible to predict exactly which shape a sheet will form, concedes Alben, “but we do know that it has to do with how strain from different areas interact.” Alben now hopes to find ways of biasing a sheet so that it buckles in a particular way. Natalio Krasnogor works on self-assembly at Nottingham University, UK. “The idea of using origami-style methods is neat,” he says, “but it is currently limited to cases where it is easy to predict the type of interactions that will happen and the possible outcomes.” Journal reference: Physical Review Letters (10.1103/PhysRevE.75.056113) More on these topics: