Cotton t-shirts could soon charge electronic gadgets

Mechanical engineers are working on how to turn the material in a cotton T-shirt into a source of electrical power.

Xiaodong Li, from the University of South Carolina, envisions integration of the cell phone and just about every electronic gadget into our lives.

In fact, Li sees a future where electronics are part of our wardrobe.

"We wear fabric every day," Li said.

"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," he said.

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 and could be folded without breaking.

"We will soon see roll-up cell phones and laptop computers on the market," Li said. But a flexible energy storage device is needed to make this possible," he said.

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 activated carbon textile acts like double-layer capacitors, which are also called a supercapacitors because they can have 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 nanometer thick, this layer of manganese oxide greatly enhanced the electrode performance of the fabric.

"This created a stable, high-performing supercapacitor," Li said.

This hybrid fabric, in which the activated carbon textile fibres are coated with nanostructured manganese oxide, improved the energy storage capability beyond the activated carbon textile alone.

The hybrid supercapacitors were resilient even after thousands of charge-discharge cycles, performance didn't diminish more than 5 percent.

"By stacking these supercapacitors up, we should be able to charge portable electronic devices such as cell phones," Li added.

The study has been published in the journal Advanced Materials.