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 the April 19, 2017 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. The researchers expect this technology to pave the way to enhance other forms of energy storage and printable, stretchable electronics, including for Lithium-ion batteries, super capacitors and photovoltaic cells.

The prototype battery the researchers developed has about 20 percent of 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 3 Volt LED.

The researchers are now working to improve the battery's performance and expand the use of the technology to different applications, such as solar and fuel cells.

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.

The UC San Diego team is confident that their thin, stretchable batteries will replace so-called "coin batteries" in the next few years.