LAKE WALES, Fla. ‐ Printable, stretchable, flexible battery technologies could enable wearable fabrics and stretchable LED displays to carry their own power source. Researchers at the University of California at San Diego recently demonstrated an example of a self-powered wearable that features a newly formulated zinc-silver-oxide rechargeable battery technology.
The stretchable battery (here the "Nano" letters) can be printed onto any fabric and stretched up to twice its size without affecting its storage capacity, current delivery or rechargability.
However, after experimenting with a different formulation, Meng, who is director of the Sustainable Power and Energy Center at UCSD, discovered that adding bismuth oxide -- which also works for next-generation lithium oxygen batteries too -- prevents zinc salts from forming permitting the zinc oxide battery to have a long life as well as be rechargeable.
Rajan Kumar is one of the authors of the Advanced Energy Materials paper and leads a team to commercialize the technology.
Meng's discovery enabled Wang's group to create the stretchable zinc oxide battery that can be printed on fabrics to supply them with a rechargeable power source, enabling wearables to have self-powered LED displays.
The researchers demonstrated that possibility by printing the zinc oxide batteries on t-shirts forming the word "Nano" powering a green LED.
The zinc silver oxide ink was made more durable by mixing it with isoprene (a derivative of rubber) and styrene, allowing it to be stretched to twice its size without deformation or diminished output. However, its capacity was only about a fifth of that in a coin cell battery.
The battery is only one-tenth the thickness of a coin cell, cheaper to manufacture and of course easier to apply to stretchable fabrics. Its cost, when printed in dual-formations (since each cell produces only 1.5 volts, requiring two to power 3V LEDs) was just half a dollar compared to as much as $5 for a rechargeable coin cell, according to the team).
Next the researchers plan to increase the battery's power density, experiment with different formulations to outperform coin cells at a fraction of their price, as well as try to reformulate lithium-ion style batteries, supercapacitors and photovoltaic cells for stretchability. They also plan to print them on transparent substrates that can be applied to the skin.
The projects will be funded by new technology accelerator at UC San Diego run by the Institute for the Global Entrepreneur, which is also administering the National Science Foundation (NSF) Innovation-Corps (I-Corps) program at UCSD.
— R. Colin Johnson, Advanced Technology Editor, EE Times