Scientists foresee a time when medical monitoring devices are integrated seamlessly into the human body, tracking a patient’s vital signs and transmitting them to the respective physician. Gone would be the days of frequent doctor and hospital visits. But up until now, electronics have been too rigid. This challenge may soon be a thing of the past now that researchers at the McCormick School of Engineering have developed a design that allows electronics to bend and stretch to more than 200% their original size, four times higher than with existing technology. This can be achieved by combining a porous polymer and liquid metal.
A paper about the findings, “Three-dimensional Nanonetworks for Giant Stretchability in Dielectrics and Conductors,” was published June 26 in the journal Nature Communications.
“With current technology, electronics are able to stretch a small amount, but many potential applications require a device to stretch like a rubber band,” said Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering, who conducted the research with partners at the Korea Advanced Institute of Science and Technology (South Korea), Dalian University of Technology (China), and the University of Illinois at Urbana-Champaign. “With that level of stretchability we could see medical devices integrated into the human body.”
One of the challenges the researchers had to overcome was a loss of conductivity in stretchable electronics. Circuits made from solid metals that are on the market today can survive a small amount of stretch, but their electrical conductivity plummets by 100 times when stretched. “This conductivity loss really defeats the point of stretchable electronics,” Huang said. To overcome these challenges, they created a highly porous three-dimensional structure using a polymer material, poly(dimethylsiloxane) (PDMS), that can stretch to three times its original size. Then they placed a liquid metal (EGaIn) inside the pores, allowing electricity to flow consistently even when the material is excessively stretched.
The result was a material that is both highly stretchable and extremely conductive.
“By combining a liquid metal in a porous polymer, we achieved 200 percent stretchability in a material that does not suffer from stretch,” Huang said. “Once you achieve that technology, any electronic can behave like a rubber band.”Yvonne Klöpping