February 27, 2013
New Battery Could Stretch Its Way Into Samsung’s Flex Display
[WATCH VIDEO: Stretchable, Rechargeable Lithium-Ion Battery]
Lee Rannals for redOrbit.com — Your Universe Online
Northwestern University's Yonggang Huang and the University of Illinois' John A. Rogers have created the world's first stretchable lithium-ion battery. They reported in the journal Nature Communications about how their new device would be able to be used in stretchable, or flexible, electronics devices.
The two researchers showed off how their battery continues to hold up, by powering a light-emitting diode (LED), even when it is being folded, stretched and flexed around.
"The developed microscale stretchable batteries are mainly envisioned for classes of applications in bio-integrated and related devices, where the power requirements are modest," Huang told redOrbit in an email. "The most fascinating part of the study is the general idea that we present on stretchable interconnects (using 'self-similar' serpentine design), which is broadly valuable, beyond batteries, to various kinds of electronic and optoelectronic systems."
This new technology allows for true integration of electronics and power into a small, stretchable package. Huang said they started off with a lot of battery components side by side, inside a very small space. Then, they connected these components with tightly packed, long wavy lines.
“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," Huang said.
The power and voltage of the battery is similar to a conventional lithium-ion battery of the same size. However, the flexible battery is able to keep running even when stretched up to 300 percent over its original size.
Huang and Rogers worked together on designing stretchable electronics but they needed a better way to power the devices. For the previous electronics, they had developed "pop-up" technology that allows circuits to bend, stretch and twist. The two created an array of tiny circuit elements connected by metal wire "pop-up bridges." This technique works well for circuits, but not for stretchable batteries.
The battery components needed to be packed-in tightly together, and a lot of space is needed in between components of the "pop-up" interconnect to work. For a solution, they used metal wire interconnects that are long, wavy lines, filling in the small space between battery components.
They refer to this mechanism as a "spring within a spring." Once the battery is stretched, the large "S" stretches out, and then disappears, leaving a line of small squiggles.
“We call this ordered unraveling,” Huang said. “And this is how we can produce a battery that stretches up to 300 percent of its original size.”