Band-Aid-Like Battery Pack Aimed at Wearables

Researchers have been trying to find more user- and design-friendly ways to incorporate power sources into wearable technology. While some researchers are looking to harvest energy rather than use batteries, others are trying to create sleeker, smaller and more suitable batteries.

A team of researchers at the University of Illinois at Urbana-Champaign has combined these two approaches by developing a lightweight, solar-energy-harvesting mesh of batteries that stretches, making it a more comfortable fit for wearable technology.

The team led by John Rogers, a physical chemist and materials scientist at the university, designed the device -- which has been compared to a Band-Aid because it sticks to surfaces like a Band-Aid sticks to skin -- using “the latest and best lithium-ion technology,” he told Design News. “In that sense, we don't give up anything in terms of performance compared to state-of-the-art, rigid, bulky batteries,” Rogers said.

John Rogers, a physical chemist and materials scientist, led the team that designed the device, which has been compared to a Band-Aid because it sticks to surfaces like a Band-Aid sticks to skin.
(Source: University of Illinois, Urbana-Champaign)

The team was inspired to design the battery because existing options for electrical power generation and storage in wearable electronics aren’t well-suited to the soft, stretchy mechanics of the devices themselves, he and the team wrote in an abstract for an article about the technology published in the journal, Proceedings of the National Academy of Sciences.

“We, and others, believe that the next generation of wearables will be thin, soft, and skin-conformal, to provide a direct interface to the skin, with capabilities in clinical-quality, continuous health monitoring,” Rogers said. “Power supply systems represent a critical need for such systems.”

The team designed the mesh using thin tiles of lithium-ion batteries held together by a soft elastomer, using long wires that allow for space to bend and stretch, he said.

“We use ultra-miniaturized, thin millimeter-scale components that we interconnect into tiled arrays using micro-scale, spring-like wiring,” Rogers told us. “When sealed in a soft elastomer material in mechanics layouts guided by theoretical computation, the resulting systems are soft, bendy, and stretchy.”

Each millimeter-scale battery element provides about 0.1 milliampere hour of power; the total power of the pack depends on the number of such elements in the tiled arrays, he said.

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But the team didn’t stop there in terms of potential power or other functionality. The device also includes tiny solar panels on top of the battery cells as well as sensors across the elastomer sheet surrounding the batteries. The solar cells power the sensors, which can provide bio-sensor data from whatever wearable the battery pack is powering. This feature can be useful for health- and medical-related wearable technology that are based on providing user feedback.

Rogers and the team continue to work on the battery packs to combine them with photovoltaic systems and control electronics with the aim of building “smart power supplies that can continuously harvest power from ambient light,” he said. Looking down the line, commercial availability for the device could happen within two years’ time, thanks to a partnership with MC10, a company already developing soft wearables, Rogers added.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.