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Bendable, Stretchy Batteries Pack Power Into Apparel

CEO: Rajan Kumar

Revenue: Pre-revenue

No. of local employees: Four

Investors: Institute for the Global Entrepreneur, Rajan Kumar

Headquarters: UC San Diego

Year founded: 2017

What makes the company innovative: Ocella produces rechargeable batteries made with an innovative polymer (made of polystyrene and isoprene) that makes them stretchable and form-fitting.

Batteries and Spandex go together like ….

Well, they go together. With a little innovation, they go together quite well.

So says Rajan Kumar, a doctoral student in UC San Diego’s nanoengineering program who has started a business that specializes in flexible, form-fitting batteries, which can stretch to twice their size and not lose their capability.

The business is called Ocella, after a phenomenon created by nanostructures found in butterflies. It is a nod to early work that Kumar did with MEMS, or micro electrical mechanical systems, which are incredibly small structures that change color as they subtly change position. Anyone who has seen a butterfly’s wings shimmer has seen the same phenomenon in nature.

Ocella’s batteries are also safe since they are made of zinc silver oxide instead of lithium.

The batteries begin their lives as a special conductive ink, which can be printed on fabric or other material. Engineers mix an innovative polymer (developed at UC San Diego) with the zinc to make a self-assembled nanostructure that is very elastic.

These batteries are not one-hit wonders, either. Adding some bismuth oxide to the mix makes the batteries rechargeable.

“We used traditional materials,” Kumar said. “There are no fancy nanomaterials. It’s simple and cheap.” (Fancy nanomaterials might be a future research project.)

The zinc batteries could be “dirt cheap,” Kumar added, thanks to inexpensive materials and printing technology. The nanotechnology lab where Kumar works includes a machine that can print a paper-thin battery on fabric or other materials. The process is similar to the silkscreens that people use to make custom-printed T-shirts.

Sensors Everywhere

Kumar talked about the technology as a life extender. Putting batteries into the flexible band of a smartwatch could add five to 10 hours to the device’s life, he said.

A wearable battery that stretches and bends with a wearer’s body might power a variety of other electronics. Kumar said he recently saw an adhesive baby thermometer with a printed battery at a drugstore. However, that battery wasn’t rechargable.

Kumar sees possibilities with the internet of things. More and more, common everyday devices from thermostats to teapots will be connected to the internet. The vision, Kumar said, is to have billions of sensors everywhere.

Printable zinc batteries could have military applications as well. Company officials plan to present at the Defense Energy Technology Challenge in Hawaii in July.

The flexible, stretchable, rechargeable battery might be one of those inventions that is still so new that inventors have not thought of all the applications yet.

For now at least, such batteries won’t be able to light neighborhoods or power automobiles. Ocella’s battery has roughly 20 percent of the capacity of a rechargeable hearing aid battery.

Two batteries can power a 3-volt light emitting diode.

Wash and Wear? Maybe Not

Ocella was one of five companies recently accepted into the UC San Diego accelerator program called the Institute for the Global Entrepreneur.

The accelerator offers $50,000 to improve prototypes and to test them with users (including strategic partners). Participating companies also get another $25,000 worth of expertise and access to university facilities.

There is plenty of work ahead. Part of it will be in customer research, delving into who might buy such an invention, Kumar said. Improving performance and durability are also on the agenda.

One issue is whether a battery could survive the washing machine. How might it stand up to detergents or heat? It could be that a printable battery might be better suited for something a person would never throw in the wash, such as a leather jacket.

The inventors might also take another look at lithium as part of their research.

Kumar, 25, did his undergraduate work at the SUNY Polytechnic Institute in Albany, N.Y. He is getting his Ph.D. at UC San Diego in printed electronics. He has a National Science Foundation graduate research fellowship, which he says gives him a certain element of freedom in his research.

He works in the nanobioelectronics lab run by Professor Joseph Wang, which is at work on a variety of projects. Wang is nanoengineering department chair and head of the university’s Center for Wearable Sensors.

The place investigates other forms of energy, including lactate to energy. Yes, you can harvest energy from sweaty socks, or take advantage of a sweat-powered Bluetooth wireless connection.

The lab is also exploring a concept for textiles called an energy sandwich. Imagine a substance with three layers. The layers on the outside of the stack could harvest solar energy on one side and thermoelectric energy on the other. Both would feed the middle layer: a flexible battery.


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