Spray-on ‘metallic’ plastic could be used for wearable electronics | Wearable technology

A plastic material that has metallic properties and remains stable even when heated, chilled, left in the air or exposed to acid has been revealed, with researchers saying it could prove valuable in wearable electronics.

What’s more, the material can be made into any shape, the researchers say.

“It’s a dark black powder. However, when we put it on a surface as a film, or press it like Play-Doh, it becomes iridescent and shiny,” said Dr John Anderson, senior author of the research from the University of Chicago.

“From what we can tell, it’s stable up to [about] 250 degrees celsius,” he added, noting the material has a conductivity similar to graphite.

Electrical conductivity occurs in materials in which electrons can flow freely. But it has traditionally been thought that a key feature of solid conductive materials is an ordered structure.

However the new substance, a metallopolymer formed of chains of molecules made of sulphur, carbon and hydrogen that carry nickel at regular intervals, has been shown to be highly conductive, despite being amorphous.

The team say there isn’t a solid theory to explain the material’s properties. But writing in the journal Nature, the researchers say they think chains of polymer form disordered stacks. One way of thinking about this is to imagine a messy pile of playing cards. The stacks pack together in a disordered fashion, creating a material that is amorphous but still allows electrons to flow both horizontally and vertically.

“While we don’t have a really clear picture yet, we think that the molecular design of the chains enables strong overlap and metallic character, even when it’s disordered and amorphous,” said Anderson.

The team say the material could prove valuable in a range of applications.

“We envision that these materials can be more robust electrical conductors, and they may be easily sprayed or painted onto surfaces or other devices,” said Anderson.

Mark Miodownik, professor of materials and society at University College London, who was not involved in the work, welcomed the research.

“Designing flexible polymers that can conduct electricity continues to be a longstanding problem, they open the door to wearable electronics and many other flexible applications,” he said. “This work opens up a new theoretical approach to designing this category of materials using molecular scale calculations.”

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