Stretchable battery for flexible circuits
Researchers at Northwestern University and the University of Illinois at Urbana-Champaign have developed stretchable batteries that can be used to power a new generation of flexible electronics. The batteries will allow stretchable electronic devices to be used anywhere, including inside the human body where they could monitor anything from brain waves to heart activity, succeeding where flat, rigid batteries would fail.
As reported in the journal Nature Communications, the flexible lithium-ion battery completes the flexible electronics package with a cordless power source.
"Batteries are particularly challenging because, unlike electronics, it's difficult to scale down their dimensions without significantly reducing performance," Rodgers told BBC News.
"We start with a lot of battery components side by side in a very small space, and we connect them with tightly packed, long wavy lines," Huang said. "These wires provide the flexibility. When we stretch the battery, the wavy interconnecting lines unfurl, much like yarn unspooling. And we can stretch the device a great deal and still have a working battery."
The battery can work for eight to nine hours and can then be recharged wirelessly, they said.
In the paper, researchers introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual ‘self-similar’ interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of ~1.1 mAh cm−2. Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.
Renowned for their pioneering work with semiconductor materials and flexible, stretchable electronics, Rogers and his colleagues have applied their expertise to devise technology solutions across such broad fields as solar power, biointegrated electronics, sensing, thin film metrology, and fiber optics. Incorporating battery power into these flexible systems closes the loop that will enable the technology to be used broadly. Initial targets for the technology include medical applications, but there are other applications for bendy batteries such as wearable solar cells and electric-eye cameras that can produce studio-quality photographs.
Contact: John A. Rogers, Department of Materials Science and Engineering, 217/244-4979.
Images: Yonggang Huang
If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, writer/editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-7716.