As scientists look for more ways of powering our future without reliance on fossil fuels, one potential avenue for generating energy is the development of foldable and wearable power sources. The idea is that these could be incorporated into clothes and other fabrics, providing a source of energy on the move.
This is a pretty big challenge, but one that doesn’t faze a team of researchers from the Georgia Institute of Technology, who have been busy creating a fabric which can harness energy from both sunshine and motion.
Upon first glance the fabric itself looks deceptively normal, with sections of glistening threads interspersed with wool. It is these glittering strands which are the powerhouses of the fabric:
The micro cable solar cells are made from lightweight polymer fibers, which were then coated with copper. This was then layered with manganese, zinc-oxide and copper iodide. The zinc oxide is photovoltaic whilst the copper helps harvest the charge. These solar cell micro cables were then woven together with copper wire. The result is the creation of a fabric which can harness the energy from ambient sunlight.
Next the strands designed to harvest motion were developed. These are based on triboelectric nanogenerators, whereby electricity is generated through the friction experienced as the fabric moves. Again, a copper wire was used but this time woven in with copper-coated polytetrafluroethylene strips.
These threads are then woven with wool to form an innocuous looking fabric with very special properties. This is done using a commercial weaving machine. The advantage of this is that no specialized equipment is needed.
Zhong Lin Wang, a Regents professor and lead member of the team, suggested that this fabric could be used to charge smart phones or GPS units in remote locations. The fabric is highly flexible, breathable and lightweight which means that its use could easily be incorporated into a wide range of items.
Wang and his team have thought carefully about how to design this fabric to make it affordable and accessible. Wang said “the backbone of the textile is made of commonly-used polymer materials that are inexpensive to make and environmentally friendly. The electrodes are also made through a low cost process, which makes it possible to use large-scale manufacturing.”
Under tests, the researchers found that a piece of textile measuring 4cm by 5cm could charge a 2mF commercial capacitor up to 2V in one minute. This was in ambient sunlight and whilst subject to mechanical excitation (wind blowing or human movement). The team also created a small flag out of the fabric and found that it generated a significant amount of power when attached to a moving car on a cloudy day.
It is hoped that the textile could be used to continuously power an electronic watch or directly charge a cell phone.
The team have integrated the material into many everyday fabrics including curtains and tents, both subject to movement and sunlight on a frequent basis. The next steps in the development of this fabric is now to study its long term durability of the fabric along with developing a similarly lightweight and durable waterproof coating in order to protect the electrical components from rain and moisture.
Top image: A sample of the fabric material. Source: FeedSquared Media