Advance could lead to flexible medical electronic implants

Researchers have developed a design that allows electronics to bend and stretch to more than 200 per cent of their original size — four times greater than is possible with today’s technology.

The advance, from Northwestern University’s McCormick School of Engineering, could lead to the development of flexible monitoring devices integrated into the body that track and transmit a patient’s vital signs.

The key is said to be a combination of a porous polymer and liquid metal.

‘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. ‘With that level of stretchability, we could see medical devices integrated into the human body.’

According to a statement, Huang and collaborators have developed electronics with about 50 per cent stretchability, although this is not high enough for many applications.

One challenge facing these researchers has been overcoming 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 drops by 100 times when stretched.

‘This conductivity loss really defeats the point of stretchable electronics,’ said Huang.

Huang’s team is said to have found a way to overcome these challenges.

First, the researchers created a highly porous three-dimensional structure using poly(dimethylsiloxane) — or PDMS — which 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 is a material that is highly stretchable and extremely conductive.

‘By combining a liquid metal in a porous polymer, we achieved 200 per cent stretchability in a material that does not suffer from stretch,’ said Huang.

‘Once you achieve that technology, any electronic can behave like a rubber band.’

A paper about the findings, ‘Three-dimensional Nanonetworks for Giant Stretchability in Dielectrics and Conductors’, was published on 26 June in the journal Nature Communications.

The research was conducted with partners at the Korea Advanced Institute of Science and Technology, China’s Dalian University of Technology and the University of Illinois at Urbana-Champaign.

Graduate student Shuodao Wang at Northwestern University is a co-author of the paper.