One key challenge for most WellTech devices is finding a way to provide electrical power. Some devices can harvest energy from their environment, using body heat, ambient light, motion, or some other source. Most devices will still require some way to store power for times when the demand exceeds supply. But a rigid battery does not always fit well in a product that is designed to conform to the human body and change its shape in response to movement.
For this reason, a recent design by researchers at Fudan University in China provides an intriguing look at the future. In an article published in the Journal of Materials Chemistry A, Huisheng Peng and his colleagues describe a new lithium-ion battery design that can be stretch up to six times its length, and then contract again, and still be able to store and release electrical energy. The new device is made by coating multiwall carbon nanotubes (MWCNT) with different lithium oxides to create anode and cathode fibers. These were then wound on a mandrel to create double-helix spring configuration. Finally, the “spring” was coated with a electrolyte gel to create a conductive layer and to keep the two fibers separated.
The two fibers remain in relative alignment in spite of being stretched as much as 600% of its original length. The device has good energy capacity, testing at 91.3 mAh/g. According to the paper, the batteries maintain 88% of their original capacity even after repeated stretching and recharging cycles.
This stretchable fiber design and small size makes this an attractive energy storage device for wearable devices. It can be woven into textiles, or incorporated into other flexible materials.