Good-bye charging cords and batteries. Wearable electronics such as the Apple Watch might soon power themselves with a clean, portable energy source: human motion.

If cutting-edge nano science pans out, limited battery life may no longer be the bugaboo of everyday technology. At universities worldwide, researchers are finding new ways to produce power from walking, typing, and other basic activities.

Their progress, documented in at least 146 scientific papers in the last three years, holds promise not only for wearable devices but also for keyboards, smartphones, laptops, and biomedical applications such as robotic skins.

"Self-powered electronics will play a critical role in the Internet of Things," in which people and devices are seamlessly connected, says Zhong Lin Wang, a leading researcher in nanotechnology as regents' professor of engineering at Georgia Institute of Technology. (Read about how scientists also develop nanobatteries.)

The basic principlestatic electricityis ancient. It focuses on the friction that occurs when two dissimilar materials touch each other. It's basically the spark that can occur when combing your hair, putting on a freshly laundered fleece in winter, or touching a doorknob after shuffling across carpet.

What's new are the minuscule materials, typically a fraction of the width of human hair. The result: Nanogenerators that are triboelectric, which stems from the Greek word for "rub."

A new backpack device harnesses the energy created by people walking to light more than 40 commercial LEDs.

The latest example is a flexible and foldable cloth that, in lab experiments, powered LEDs, a liquid crystal display, and a vehicle's keyless-entry remote. Here's how it worked: A team of Korean and Australian researchers stacked together four pieces of this clothcoated with nanorods and a silicon-based organic materialand then pushed down on the material and captured the energy generated from that pressure.

"The cloth worked for more than 12,000 cycles, showing very good mechanical durability," says Sang-Woo Kim of Korea's Sungkyunkwan University, lead author of a paper that was published last month in the peer-reviewed journal ACS Nano.

"Cost is not a big hurdle for commercialization," he says, noting the materials are inexpensive. Yet the smart cloth needs to be washable, so his team is pursuing "novel technology" to make it waterproof.

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Wearable Electronics' Newest Wrinkle: Power-Producing Cloth