A new fiber inspired by the electricity-generating cells in electric eels could power wearable devices. The fibers (shown in the schematic above) combine conducting carbon nanotubes with insulating rubber wires and electrolyte gel to create tiny capacitors. The capacitors are placed in series to generate large voltage. At bottom, scanning electron micrograph images of the new fibers.
Credit: H. Sun et al, Advanced Materials
Stretchy fibers that mimic electric eels could be woven into clothing to power wearable technology one day, new research suggests.
In experiments, these flexible fibers produced enough power to run electronic lights and watches.
The new fiber is exciting because it takes a page from nature to “solve real-world problems and even surmount nature in some aspects,” said study lead author Hao Sun, a materials scientistat Fudan University in Shanghai.
Electric eels (Electrophorus electricus) can generate deadly shocks to stun prey and defend against predators. These fish have cells known as electrocytes, which store and release electrically charged ions to generate powerful electric fields.
By themselves, electrocytes in electric eels generate low voltages of only about 0.15 volts. However, in eels, thousands of these disclike electrocytes line up, working in concert to produce deadly shocks of up to 600 volts, or about five times the voltage emitted from a U.S. electrical outlet.
Sun and his colleagues wanted to harness the power of the electric eel in a man-made material. To do so, they created fibers that mimicked the shocking creatures’ ability to stack up tiny voltage-producing cells in concert.
These fibers are capacitors, meaning they alternate pairs of electrical conductors and electrical insulators, or materials that block the flow of electricity. Capacitors store electric charge on the surfaces of the conductors, and can capture and release energy much more quickly than batteries can, although they usually store less energy than batteries do.
The scientists fabricated the capacitors by first wrapping sheets of carbon nanotubes around elastic rubber fibers 500 microns wide, or about five times the average width of a human hair. Carbon nanotubes are pipes only nanometers, or billionths of a meter, in diameter that possess remarkable electrical and mechanical properties.
The researchers made sure that the electrically conductive carbon nanotube sheets did not completely cover the electrically insulating rubber. Instead, there were gaps where the insulating rubber was exposed. Such gaps are key, because capacitors consist of both conductive and insulating units.
Then, the scientists applied patches of electrically conductive electrolyte gel onto these fibers. The pattern of patches the researchers used converted the fibers into capacitors.
The more alternating segments of electrically conductive nanotube sheets and electrically insulating rubber gaps a fiber had, the greater the voltage it could generate. A fiber about 39 feet (12 meters) long could generate 1,000 volts, the researchers reported online Jan. 14 in thejournal Advanced Materials.
Previous research also sought to mimic electric eels by connecting many electrocytelike units together. However, those units were impractical because they were strung together with metal wires, and generally had poor flexibility, the researchers said. This new device instead connected all of its electrocytelike units together on a single fiber.
“We think these findings provide an efficient strategy for the advancement of flexible electronics and wearable devices,” Sun told Live Science.
The elastic fibers could stretch up to 70 percent more than their usual length without losing their electrical or structural properties, the researchers said. The team also showed that the fibers could be woven together with conventional elastic fibers to create fabric that could be incorporated into clothes.
The researchers suggested that the eely fibers could help power miniature electronic devices. For example, in experiments, they created energy wristbands to power electronic watches, and wove fibers into T-shirts to power 57 light-emitting diodes (LEDs). In the future, these energy fibers “might be incorporated into our daily clothes to power ourwearable devices, such as the Apple Watch and Google Glass,” Sun said.
The scientists also connected their capacitor fibers to fiber-shaped solar cells to create material that could both harvest and store energy. In experiments, these combinationfibers generated 10 volts of electricity when exposed to light — enough to power some types of small electronic devices, they said. Solar cell fibers could also recharge battery fibers in wearable devices, the researchers said.