Researchers at the University of Chicago have discovered a way to create a material that can be made like a plastic, but conducts electricity like a metal.
In a paper published in the journal Nature, the scientists explain that even though the molecular fragments of the material are jumbled and disordered, it can still conduct electricity extremely well. This goes against all of the known rules about conductivity.
“In principle, this opens up the design of a whole new class of materials that conduct electricity, are easy to shape, and are very robust in everyday conditions,” John Anderson, senior author of the study, said in a media statement.
Anderson explained that by far, the oldest and largest group of conductors are metals: copper, gold, aluminum, and so on. Then, about 50 years ago, scientists were able to create conductors made out of organic materials by using a chemical treatment known as ‘doping,’ which sprinkles in different atoms or electrons through the material.
Using this technique has proven advantageous because materials become more flexible and easier to process than traditional metals. The issue that they face, however, is that they aren’t very stable; they can lose their conductivity if exposed to moisture or if the temperature gets too high.
In terms of their basic characteristics, both organic and traditional metallic conductors share a commonality: They are made up of straight, closely packed rows of atoms or molecules. This means that electrons can easily flow through the material, much like cars on a highway. In fact, scientists thought a material had to have these straight, orderly rows in order to conduct electricity efficiently.
But recently, the study’s lead author Jiaze Xie began experimenting with nickel atoms, which he strung like pearls into a string of molecular beads made of carbon and sulphur and began testing.
To his astonishment, the material easily and strongly conducted electricity. What’s more, it was very stable.
“We heated it, chilled it, exposed it to air and humidity, and even dripped acid and base on it, and nothing happened,” Xie said. “That is enormously helpful for a device that has to function in the real world.”
But to Xie and his colleagues, the most striking thing was that the molecular structure of the material was disordered.
“From a fundamental picture, that should not be able to be a metal,” Anderson said. “There isn’t a solid theory to explain this.”
Xie, Anderson and their lab worked with other scientists to try to understand how the material can conduct electricity. After tests, simulations, and theoretical work, they think that the material forms layers like sheets in a lasagna. Even if the sheets rotate sideways, no longer forming a neat lasagna stack, electrons can still move horizontally or vertically—as long as the pieces touch.
The end result is unprecedented for a conductive material.
“It’s almost like conductive Play-Doh—you can smush it into place and it conducts electricity,” Anderson said.
The scientists are excited because the discovery suggests a fundamentally new design principle for electronics. For example, metals usually have to be melted in order to be made into the right shape for a chip or device, which limits what can be done with them, since other components of the device have to be able to withstand the heat needed to process these materials.
The new material has no such restriction because it can be made at room temperature.