Wednesday, February 20, 2008

Wearable technology:One step beyond

Despite all attempts to harness the potential for other practical use, nothing has so far materialised in wearable shoe technology. But it is not for the want of trying and may only be a matter of time. The potential for clothing and shoes to power medical implants and personal electronics is no longer as dream, according to the developers. A new innovation in nanogenerator technology involves Kevlar flexible fibres coated with tetraethoxysilane and then layered with zinc oxide. The crystals of zinc oxide grow outwards, forming crystalline rods protruding from the fibres like the hairs on a brush. The piezoelectric nanowires are grown vertically from the surface of the polymer fibre which acts as an electrode. To complete the nanogenerator Zhong Lin Wang and his colleagues built another electrode made as a platinum-coated silicon plate with parallel peaks and trenches carved on its surface. The zinc oxide nanowires convert mechanical energy into electrical voltage and according to the researchers at Georgia Institute of Technology the filaments harvest any kind of vibration or motion and turn it into for electric current. By this way walking, breathing, and heartbeats all have potential to generate power. When the electrodes are pushed together by ultrasonic waves the nanowires bent and produced current. Futher research has deveolpoed more flexible electrodes using a thin layer of gold to plate some of the fibres and these stiffer fibres push and bend the uncoated nanowires, generating more current. The potential for microscale sensors to be implanted into the body to measure biomarkers for cancer and glucose is a new and exciting innovation. The present disadvantage of implanted chemical batteries is they are bulky by comparison and have a limited lifetime. Nanogenerated biological sensors could in future be used to monitor blood pressure or muscle movement. The commercial potential to include nonogenerated sensors into ordinary clothing is still in the future although experts believe woven yarns (of multiple fibres) would generate enough power to run portable electronics. Costs are too prohibitive however and the more likely scenario is the technology will be put to military use, such as in tents and shoes. The research was sponsored by the National Science Foundation, the U.S. Department of Energy and the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology.

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