Many electronic parts are made of hard materials that break easily. That makes them tough to use in products that need to bend. Now, Sam Yoon and his team have developed a thin mesh (网状物) that can both bend and conduct electricity.
His team started out with something called acrylonitrile, a clear liquid often used to make thin plastic fibers. Yoon and his team mixed this material with another liquid, which acted as a solvent. A solvent is something that can make other substances into liquids. Then, they squeezed the mix through a very tiny pipe: As the mixture was sprayed through the air, the solvent evaporated(挥发)and the acrylonitrile molecules linked up to make long chains, creating a type of plastic known as PAN. The researchers continually squeezed the mixture through the pipe. A single long PAN fiber was created. The scientists moved the pipe back and forth as the PAN was squeezed out. It ended up creating a layer that looked something like a spider's web.
PAN, like most plastics, doesn't conduct electricity. So the team's next step would normally be to add a coating of metal so that electricity could flow through it. But it could be tough sticking such coatings on PAN. So the researchers added an extra step. They sprayed a thin coating of an inert metal onto the PAN. Inert metals, like gold, typically don't react with other materials. The researchers then added another layer of PAN fiber at the top of the first, web-like layer. They provide temporary support, helping the metal-sprayed base resist sinking during the next step.
The researchers connected the fiber-covered frame to a negatively changed electrode. Then they dipped the fiber-covered frame into a solution that included the liquid copper. The team turned on the electric current for about one minute to make it run through the solution. The copper in the solution was attached to all of the fibers. But it stuck only to those that wore a metal jacket. Besides adding a thin layer of copper that conducts electricity, this process helped bond the PAN strands together at places, where they touched each other, Yoon notes.
The researchers then attached all of the fibers to a thin, clear layer of plastic, which had sticky backing, like a Band-Aid. Finally, the team dipped all of these into a liquid that made any of the PAN fibers that lacked a copper jacket into liquids. Only thosethat can be used to conduct electricity were left. Because the fibers were very thin and widely separated, light waves easily travel through the mesh. The copper coating acted just like a wire, permitting electricity to flow freely across it.
