Wearable Tech World Feature Article
July 22, 2014

Wearable Devices Could Soon See Flexible, Printed Batteries

There are a couple of things that I learned at last year’s first Wearable Technology Expo. As impressive as a wearable device can be, if it does not have, at least, a sense of fashion you will not wear it, just as important, if it does not actually perform a useful function, you will not need it. Now, most wearable devices need to be powered and that is something that has always been problematic.

In general, you need a battery that is strong enough to power the device for the length of its use. Unfortunately, this results in a large, mostly lithium battery, such as we see in smartphones. The other problem is that when these batteries are made small enough to fit a device, such as a smartwatch, they do not have enough power to keep the device running for any realistic length of time.

Developing flexible printed batteries that can be produced in-line is considered to be one of the keys to the future of printed electronics. The ability to utilize flexible, disposable batteries will allow designers to develop new form factors that coin batteries cannot match. This is due to the fact that as mobile and wearable devices get smaller and more bendable, the batteries that power them need to keep up.

A California startup is attempting to gain a foothold in that field. Imprint Energy is a company that aims to reshape the battery landscape. The company’s goal is to remove the longstanding limitations on the recharge-ability of zinc-based batteries. This will enable the production of ultrathin, flexible, high energy density rechargeable batteries for significantly lower cost and without the design limitations or safety concerns of other battery technologies.

I mentioned lithium batteries earlier these are used in most smartphones, tablets and laptops, while the button batteries are used in watches. The problem with this type of battery is they are highly reactive and have to be protected in ways that add size and bulk.

Although zinc is more stable, the water-based electrolytes in conventional zinc batteries cause zinc to form dendrites, branch-like structures that can grow from one electrode to the other, shorting the battery. Neither of these solutions makes the batteries suitable for wearable devices.

Imprint Energy’s flexible, printed batteries are based on research that company co-founder Christine Ho began as a graduate student at the University of California, Berkeley. By collaborating with another researcher in Japan, Dr. Ho was able to produce microscopic zinc batteries using a 3-D printer (another area that has seen great improvements allowing it to be used to create wearable devices).

Image via TechnologyReview.com

The startup was able to move ahead because it secured $6 million in funding. The capital was raised from such companies as Phoenix Venture Partners and AME Cloud Ventures, in addition to previous investors which included Dow Chemical and CIA-backed venture firm In-Q-Tel.

What makes Imprint Energy’s batteries different is that Dr. Ho developed a solid polymer electrolyte. This avoids the problem mentioned above with traditional zinc batteries and also provides greater stability and greater capacity for recharging. In addition, due to zinc’s environmental stability, the company did not need the protective equipment required to make an oxygen-sensitive lithium battery. All of which is very important when using it in a wearable device.

Dr. Ho said that Imprint has been in talks about the use of flexible, printed batteries in clothes and “weird parts of your body like your eye.” The company also recently began working on a project funded by the U.S. military to make batteries for sensors that would monitor the health status of soldiers. Other potential applications include powering smart labels with sensors for tracking food and packages. You can see that use for such a product goes well beyond just one industry. One device that I can see this battery being used with is Google’s smart contact lens.

Dr. Ho mentioned that no standards had been developed to measure a flexible battery’s flexibility. It was because of this that Imprint Energy built its own test rig so that it could benchmark its batteries against commercial batteries that claimed to be flexible. According to Dr. Ho, existing batteries failed catastrophically after fewer than 1,000 bending cycles while Imprint’s batteries remained stable.

Want to learn more about the latest in wearable technology? Be sure to attend Wearable Tech Expo, July 23 & 24 at the Javits Convention Center in New York City.  Stay in touch with everything happening at the event -- follow us on Twitter.

Edited by Maurice Nagle

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