Researchers at the University of California, Berkeley, are developing a fabric that can create electrical charge through kinetic energy generated by moving and twisting the textile.
The scientists are working in a project exploring the properties of electrospun, piezoelectric nanofibres and the potential of the technology in various applications, including power scavenging, sensing and actuation.
The nanofibres can be woven in clothing that, when stretched or twisted, produces energy.
'Using a formula of organic polyvinylidene fluoride (PVDF), the nanofibre is flexible and simple to make,' explains postdoctoral researcher Liangbing Hu. 'This shows a marked improvement upon nanogenerators created using inorganic materials, which are less flexible and harder to grow.'
The polymeric nanogenerators are placed 50 micrometres apart in a grid pattern by a near-field electrospinning technique, developed by the university.
Early prototype nanofabrics have been produced that can generate up to 30 millivolts under varying strains and manipulations.
Researchers are currently trialling the robustness of the material and have reported no noticeable degradation after stretching and releasing the nanofibres for 100 minutes at a frequency of 0.5Hz.
Clothing integration
With a diameter of around 500 nanometres, the nanogenerators have been designed for 'invisible' integration into a variety of apparel.
Hu says: 'Nanofibres are so small, we could weave them right into clothes with no perceptible change in comfort for the wearer.'
Prototypes have demonstrated maximum energy conversion efficiencies of over 20%.
'We would be looking to provide fibres offering a conversion efficiency of at least 25%,' states Hu.
The university will explore the commercial options once the project has reached completion in 2011.
The university has already explored the potential of implanting nanogenerators in plastic to trickle-feed energy to a battery for higher energy needs, for instance in the medical field for implantable defibulators. The department now will focus its attention on the application of fabric-based generators.
'The obvious choice would be integration in sportswear, such as a running pant or jersey that could charge an mp3 player or phone,' adds Hu. 'There are also other applications for markets whereby the wearer is constantly mobile and reliant upon access to electronic devices, for example the military.'
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