The researchers used standard screen printing techniques to make the batteries, significantly bringing down the production costs of the technology.
Nanoengineers at the University of California San Diego have developed the first printed battery that is flexible, stretchable, and rechargeable. The zinc batteries could be used to power everything from wearable sensors to solar cells and other kinds of electronics. The work appears in an issue of Advanced Energy Materials.
The researchers made the printed batteries flexible and stretchable by incorporating a hyper-elastic polymer material made from isoprene, one of the main ingredients in rubber, and polystyrene, a resin-like component. The substance, known as SIS, allows the batteries to stretch to twice their size, in any direction, without suffering damage.
The ink used to print the batteries is made of zinc silver oxide mixed with SIS. While zinc batteries have been in use for a long time, they are typically non-rechargeable. The researchers added bismuth oxide to the batteries to make them rechargeable.
"This is a significant step toward self-powered stretchable electronics," said Joseph Wang, one of the paper’s senior authors and a nanoengineering professor at the Jacobs School of Engineering at UC San Diego, where he directs the school’s Centre for Wearable Sensors. "We expect this technology to pave the way to enhance other forms of energy storage and printable, stretchable electronics, not just for zinc-based batteries but also for Lithium-ion batteries, as well as supercapacitors and photovoltaic cells."
The prototype battery the researchers developed has about 1/5 the capacity of a rechargeable hearing aid battery. But it is 1/10 as thick, cheaper, and uses commercially available materials. It takes two of these batteries to power a 3V LED. The researchers are still working to improve the battery’s performance. Next steps include expanding the use of the technology to different applications, such as solar and fuel cells, and using the battery to power different kinds of electronic devices.
Researchers used standard screen printing techniques to make the batteries—a method that dramatically drives down the costs of the technology. Typical materials for one battery cost only $0.50. A comparable commercially available rechargeable battery costs $5.00
Batteries can be printed directly on fabric or on materials that allow wearables to adhere to the skin. They also can be printed as a strip to power a device that needs more energy. They are stable and can be worn for a long period of time.
Figure 1: For demonstration purposes, the stretchable batteries were printed on fabric. The batteries make up the word NANO on the shirt and are powering a green LED that is lit in this picture.