Stretchable electrodes pave way for flexible electronics

While flexible electronics have potential use in a variety of applications, from bendable displays to medical implants that move with the body, finding good conductors that still work when pulled to twice their length has proved a challenge for researchers. Until now. The University of Michigan team began by embedding spherical gold nanoparticles in polyurethane. "We found that nanoparticles aligned into chain form when stretching," Professor Nicholas Kotov explained. "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." The team made two versions of the material – by building it in alternating layers or filtering a liquid containing polyurethane and nanoparticle clumps to leave behind a mixed layer. Overall, they found that the layer by layer material design was more conductive. Without stretching, it had a conductivity of 11,000S/cm, on par with mercury. Furthermore, even when close to its breaking point, the layer by layer material still conducted at 2,400S/cm. The filtered material, meanwhile, had an electrical conductance of 35S/cm when pulled to an unprecedented 5.8 times its original length. Prof Kotov believes the stretchable conductors could be used in brain implants to alleviate diseases such as depression, Parkinson's and Alzheimer's. Other potential applications include flexible displays, soft robotics and flexible transistors.