Portable chargers and battery packs, also known as power banks, were revolutionary when they became popular for anyone who knew they wouldn’t be around a convenient outlet. Now, the next leap in portable batteries has been taken: You might just be able to charge your iPhone by plugging it right into your sweatshirt in the near future. University of California San Diego’s Jacobs School of Engineering unveiled its stretchable batteries that can be directly printed on just about anything. The researchers used standard screen-printing techniques to apply the battery. Made with a hyper-elastic polymer fabric, these flexible, zinc batteries are rechargeable and can stretch to twice their size without damage to the technology, which can be seen in the video below.

This innovation in wearable technology may not make it to the promotional products industry just yet, but that’s because this invention is still a prototype. However, the technology these nanoengineers developed costs 50 cents a battery because of the materials used and the standard screen-printing techniques. In comparison, a rechargeable battery pack on the market currently retails at about $5. Despite this development , there's still work to be done. UC San Diego researchers are still working on improving the battery power. As of now, it will take two of their batteries to charge a single 3 Volt LED light .

"This is a significant step toward self-powered stretchable electronics," says 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 Center 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 researchers say the 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.