Engineers have created energy-scavenging nanofibers that could one day be woven into clothing and textiles in a research by University of California, Berkeley. These nano-sized generators have "piezoelectric" properties that allow them to convert into electricity the energy created through mechanical stress, stretches and twists, leading to wearable 'smart clothes' that can power hand-held electronics through ordinary body movements. Because the nanofibers are made from organic polyvinylidene fluoride (PVDF), they are flexible and relatively easy and cheap to manufacture. Although they are still working out the exact calculations, the researchers noted that more vigorous movements, such as the kind one would create while dancing, should theoretically generate more power. Since the nanofibers are so small, they could be woven into clothes with no perceptible change in comfort for the user.
The team at UC Berkeley pioneered the near-field electrospinning technique used to create and position the polymeric nanogenerators 50 micrometers apart in a grid pattern. The technology enables greater control of the placement of the nanofibers onto a surface, allowing researchers to properly align the fiber nanogenerators so that positive and negative poles are on opposite ends, similar to the poles on a battery. Without this control, the researchers explained, the negative and positive poles might cancel each other out and reducing energy efficiency.
The researchers demonstrated energy conversion efficiencies as high as 21.8%, with an average of 12.5%. Surprisingly, the energy efficiency ratings of the nanofibers are much greater than the 0.5 to 4% achieved in typical power generators made from experimental piezoelectric PVDF thin films, and the 6.8% in nanogenerators made from zinc oxide fine wires.
The team expects efficiency to be raised further. For the preliminary results, the team sees a trend that the smaller the fiber we have, the better the energy efficiency.