The idea of e-textiles, or electronic clothing, holds much promise in the fields of sports medicine, healthcare and consumer electronics. Yet, one of the main issues is how to power sensors and other electronic components in these t-shirts, caps, braces and jackets so that it can be stretchable and flexible, while at the same time able to withstand the impact of being in a washing machine.
Researchers at the University of California, San Diego are tackling the problem of the flexible and stretchable aspect, with a printed zinc battery that incorporates a hyper-elastic polymer material made from isoprene, a component in rubber, and polystyrene.
Researchers say the flexible and stretchable battery could be used to power anything from wearable sensors, to solar cells, to other electronics. The polymer, called SIS, allows batteries to stretch to twice their size in any direction without suffering damage.
The printed battery uses ink made of zinc silver oxide mixed with the SIS polymer. While zinc batteries have been used for a while, they are typically not rechargeable; however, the researchers added bismuth oxide to the batteries to make them rechargeable.
“This is a significant step toward self-powered stretchable electronics,” says 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 prototype battery only has about one-fifth the capacity of a rechargeable hearing aid battery, but it is only one-tenth as thick, cheaper and made of commercially available materials. Two of these batteries would be needed to power a 3 volt light emitting diode (LED). Work is being done to improve the batteries performance with the next steps to include expanding the use of the technology to different applications for use in solar and fuel cells or to power other electronic devices.
Using a standard screen printing technique, the materials for one battery costs only 50 cents, compared to commercially available rechargeable battery that costs about $5.00. The batteries can be printed directly onto fabric or on materials that allow wearables to adhere to the skin. They can be printed as a strip to power a device that needs more energy.
The work to make the batteries rechargeable by mixing bismuth oxide with the zinc electrodes shows that it is possible to use small amounts of additives to charge the properties of materials. Researchers say this could be used to improve other types of batteries as well, not just zinc batteries but perhaps other electro-chemistries such as lithium-oxygen.
The full research results can be found in the journal Advanced Energy Materials