In the future, you might be able to charge your cellphone from your clothing — and your cellphone could be made of fabric that easily rolls up like paper.
These are some of the goals of Dr. Xiadong Li, a mechanical engineering professor at the University of South Carolina who believes that the next great technological innovation lies in flexible electronic devices.
Li and post-doctoral associate Lihong Bao recently devised a way to transform an ordinary cotton shirt into a source of electrical power. His team soaked a shirt in a fluoride solution, dried it and baked it at a high temperature without oxygen so it wouldn’t burn. The result was a shirt with a fabric made of activated carbon textile instead of cellulose.
“Carbon is one of the major materials for energy storage devices such as batteries and capacitors,” Li said. “Presently, we mostly rely on oil and chemical processes to produce carbon, which is expensive and not environmentally friendly. Since cotton is a green and renewable resource, we hypothesized that simple cotton T-shirts could be a possible candidate for a carbon source.”
However unlike some types of carbon, the activated carbon textile retained its original flexibility, allowing the T-shirt to still be folded without breaking.
Li used small swatches of the T-shirt’s fabric as an electrode and found that they acted as capacitors, the components of electronic devices that store electrical charges. The activated carbon textile acts like supercapacitors, which have high energy-storage densities, making the fabric a repository for electricity.
“We developed a simple route to convert a cotton T-shirt into a flexible energy device — a supercapacitor. This is a low-cost, green technology that is also a new and innovative biotechnology,” Li said.
Li and Bao then took the fabric a step further by coating the individual fibers with “nanoflowers” of manganese oxide. This enhanced the activated carbon textile’s performance and created “a stable, high-performing supercapacitor,” according to Li.
The “nanoflowers” improved the hybrid fabric’s energy-storage capability, and its supercapacitors were resilient. After thousands of charge-discharge cycles, the fabric’s performance didn’t diminish more than 5 percent.
By improving the means of creating activated carbon fibers, Li says his team has created a more eco-friendly process.
"Previous methods used oil or environmentally unfriendly chemicals as starting materials. Those processes are complicated and produce harmful side products. Our method is a very inexpensive, green process," Li said.
How exactly can this research be used in the future? In addition to roll-up cellphones and electronics we can wear, Li says there are a variety of other applications.
“Almost anything that requires an energy storage source would be applicable. Portable electronic devices and wearable electronics, such as roll-up displays, implanted medical devices, active radio-frequency identification tags and integrated-circuit smart cards,” he said.
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