MIT Engineers Produce the World’s Longest Flexible Fiber Battery - highlights

MIT engineers produce the world’s longest flexible fiber battery The rechargeable battery can be woven and washed, and could provide power for fiber-based electronic devices and sensors.

MIT postdoc Tural Khudiyev (now an assistant professor at National University of Singapore), former MIT postdoc Jung Tae Lee (now a professor at Kyung Hee University), and Benjamin Jean-baptiste Grena SM ’13, PhD ’17 (currently at Apple) are the lead authors on the paper.

Researchers, including members of this team, have previously demonstrated fibers that contain a wide variety of electronic components, including light emitting diodes (LEDs), photosensors, communications, and digital systems. Many of these are weavable and washable, making them practical for use in wearable products

The new fiber battery is manufactured using novel battery gels and a standard fiber-drawing system that starts with a larger cylinder containing all the components and then heats it to just below its melting point. The material is drawn through a narrow opening to compress all the parts to a fraction of their original diameter, while maintaining all the original arrangement of parts.

While others have attempted to make batteries in fiber form, Khudiyev says, those were structured with key materials on the outside of the fiber, whereas this system embeds the lithium and other materials inside the fiber, with a protective outside coating, thus directly making this version stable and waterproof. This is the first demonstration of a sub-kilometer long fiber battery which is both sufficiently long and highly durable to have practical applications, he says.

A demonstration device using the new fiber battery incorporated a “Li-Fi” communications system — one in which pulses of light are used to transmit data, and included a microphone, pre-amp, transistor, and diodes to establish an optical data link between two woven fabric devices.

The 140-meter fiber produced so far has an energy storage capacity of 123 milliamp-hours, which can charge smartwatches or phones, he says.

“The beauty of our approach is that we can embed multiple devices in an individual fiber, Lee says, “unlike other approaches which need integration of multiple fiber devices.” They demonstrated integration of LED and Li-ion battery in a single fiber and he believes more than three or four devices can be combinded in such a small space in the future. “When we integrate these fibers containing multi-devices, the aggragate will advance the realization of a compact fabric computer.”

In addition to individual one-dimensional fibers, which can be woven to produce two-dimensional fabrics, the material can also be used in 3D printing or custom-shape systems to create solid objects, such as casings that could provide both the structure of a device and its power source.