"This is a significant step toward self-powered stretchable electronics," said Joseph Wang, a nanoengineering professor at the Jacobs School of Engineering at UC San Diego.
"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 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. The researchers added bismuth oxide to the batteries' zinc electrodes to make them rechargeable.
The researchers used standard screen printing techniques to make the batteries – a method that is said to drive down costs. The team claims typical materials for one battery cost $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. According to the researchers, they are stable and can be worn for long periods.