Researchers have found it’s possible to turn a t-shirt into a phone charger by successfully transforming cotton into a flexible, highly conductive component.
The idea for creating “electrical” clothing for Professor Xiaodong Li and researcher Lihong Baofrom the University of South Carolina, stemmed from the idea that phones were once limited to households, then moved to cars and later into pockets.
“We wear fabric every day,” said Li on the university website. “One day our cotton T-shirts could have more functions; for example, a flexible energy storage device that could charge your cell phone or your iPad.”
Starting with a T-shirt from a local discount store, Li’s team soaked it in a solution of fluoride, dried it and baked it at high temperature. They excluded oxygen in the oven to prevent the material from charring or simply combusting.
The surfaces of the resulting fibres in the fabric were shown by infrared spectroscopy to have been converted from cellulose to activated carbon. Yet the material retained flexibility; it could be folded without breaking.
The once-cotton T-shirt proved to be a repository for electricity. By using small swatches of the fabric as an electrode, the researchers showed that the flexible material, which Li’s team terms activated carbon textile, acts as a capacitor. Capacitors are components of nearly every electronic device on the market, and they have the ability to store electrical charge.
Moreover, Li reports that the activated carbon textile acts like double-layer capacitors, which are also called super-capacitors because they possess particularly high energy storage densities.
But Li and Bao took the material even further than that. They then coated the individual fibres in the activated carbon textile with ‘nanoflowers’ of manganese oxide. Just a nanometre thick, the layer of manganese oxide greatly enhanced the electrode performance of the fabric. “This created a stable, high-performing super-capacitor,” Li explained.
This hybrid fabric improved the energy storage capability beyond the activated carbon textile alone, the super-capacitors were resilient: even after thousands of charge-discharge cycles, performance didn’t diminish more than 5 percent.
“By stacking these super-capacitors up, we should be able to charge portable electronic devices such as cell phones,” Li said.
Li is particularly pleased to have improved on the means by which activated carbon fibres are usually obtained. “Previous methods used oil or environmentally unfriendly chemicals as starting materials,” he said. “Those processes are complicated and produce harmful side products. Our method is a very inexpensive, green process.”