A newly developed prototype for a wearable, elastic battery mimics the structure of biological DNA and could better meet growing demand sparked by advancements in robotics and a rising interest in smartwatches, sleep-monitoring devices and other technology-driven fashions and medical tools.
Known for its characteristic coiled configuration, DNA's design can hold tons of genetic information, is flexible enough to fit into the minuscule space of a cell and still remains mechanically sound. Aspiring to emulate that triple benefit, researchers proposed a battery of similar structure in a paper published April 2 in Nano Energy.
Study author Changsoon Choi, an assistant professor in the Department of Energy and Materials Engineering at Dongguk University in Seoul, told The Academic Times that his team's DNA-lookalike batteries can be employed for devices that call for an alternative to traditionally bulky three-dimensional types, such as the AA battery.
"The ultra-high stretchability and capacity of supercoil battery suggests many promising applications," Choi said. He mentioned smart clothes, wearable devices, highly elastic electronics and flexible and precise technology in space, as well as exoskeletons, or robotic limbs, such as "arms with an extreme reach."
The special structure of DNA is referred to as a double helix. Each initial coil is coiled a second time, and the combination is called a supercoil. That compresses the nucleic acid such that many of its components, and plenty of genetic information, can be included in a small amount of space.
This unique structure "effectively stores the genetic code of organism in the limited space of cell by condensing down and packing its molecule chains in a series of structural steps," Choi explained. That, he relayed, "inspired our research team to realize the fiber battery with high stretchability and energy-storage capacity."
In a comparable manner, the team "supercoiled" battery fibers, condensing them so efficiently that significantly long ones could be used for small, compact devices, because they would now fit. That expands the region available to load active material, the electrically conductive material that makes the battery work.
"The supercoiling provides an additional structural transformation to pack the electrode length into coil — and supercoil — loops more effectively," Choi said.
It also greatly improved elasticity, according to the study: The supercoiled battery had a stretchability of 800%. That means it can simultaneously possess optimal energy storage performance and safely undergo physical deformation, including the inevitable movement of the fabric when a person wears it, such as with sleep-monitoring bracelets.
"The final length of the electrode was only 29% of its initial length after supercoiling," Choi said, "which dramatically improved not only stretchability [but] also the active material loading density, and finally realized a device with both excellent mechanical stretchability and energy storage capacity."
He added that the team even, "successfully fabricated a supercoil battery electrode with uniform diameter and electrical properties using 3 meter-long spandex fiber."
The innovative approach is a much-needed departure from current methods of developing stretchable batteries, the paper says. That's because there's typically a trade-off between stretchability and space to load active material.
"Current methods commonly use a buckle (wrinkle) structure, which is made of wrapping a stiff active material around the stretchable core fiber," Choi explained. "Although this fabrication method results [in] moderately stretchable electrodes, the substrate, which is the bulk of the fiber, cannot participate in the loading sites for the active material."
However, Choi noted that one potential limitation with his team's DNA-inspired battery is that the conductive material it requires, made of carbon nanotubes, is pricey.
"It is difficult to find and select a substrate material that has sufficient mechanical strength and toughness, because the fiber must endure enormous torsional stress and deformation during the continuous twisting process," he noted, "The conductive [carbon nanotube] sheath, which is still expensive, is also the limitation that must be solved with unceasing research."
The paper, "DNA-inspired, highly packed supercoil battery for ultra-high stretchability and capacity," published April 2 in Nano Energy, was authored by Jae Myeong Lee, Changsoon Choi, Young-Kwan Kim and Wonkyeong Son, Dongguk University-Seoul; Younghoon Kim and Sang Kyoo Lim, Daegu Gyeongbuk Institute of Science and Technology; Sungwoo Chun, Korea University; Dongseok Suh, Sungkyunkwan University; Shi Hyeong Kim, Korea Institute of Industrial Technology; Hyun Kim, CCDC Army Research Laboratory; and Dongyun Lee, Pusan National University.