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Gold-studded polyurethane can better conduct electricity

Posted: 19 Jul 2013 ?? ?Print Version ?Bookmark and Share

Keywords:flexible electronics? conductors? stretchable electrodes?

Engineering researchers at the University of Michigan discovered that spherical gold nanoparticles embedded in polyurethane could outcompete conductors such as wires in tortuous zigzag or spring-like patterns, liquid metals and nanowire networks in terms of stretchability and concentration of electrons.

"Essentially the new nanoparticle materials behave as elastic metals. It's just the start of a new family of materials that can be made from a large variety of nanoparticles for a wide range of applications," said Professor Nicholas Kotov.

"We found that nanoparticles aligned into chain form when stretching. That can make excellent conducting pathways," said Yoonseob Kim, first author of the study and a graduate student in the Kotov lab.

The team took state-of-the-art electron microscope images of the materials at various tensions to find out what happened as the material stretched. The nanoparticles started out dispersed, but under strain, they could filter through the minuscule gaps in the polyurethane, connecting in chains as they would in a solution.

Polyurethane studded with gold nanoparticles

Figure 1: Polyurethane studded with gold nanoparticles can conduct electricity even when stretched to more than twice its original length. Image credit: Joseph Xu.

"As we stretch, they rearrange themselves to maintain the conductivity, and this is the reason why we got the amazing combination of stretchability and electrical conductivity," Kotov said.

The team made two versions of their material-by building it in alternating layers or filtering a liquid containing polyurethane and nanoparticle clumps to leave behind a mixed layer. Overall, the layer-by-layer material design is more conductive while the filtered method makes for extremely supple materials. Without stretching, the layer-by-layer material with five gold layers has a conductance of 11,000 Siemens per centimeter (S/cm), on par with mercury, while five layers of the filtered material came in at 1,800 S/cm, more akin to good plastic conductors.

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