Wednesday, June 30, 2010

On shoes that may harvest pounding of walking to power mobile phones-

Tue, Feb 16, 2010

Washington, Feb 16 (ANI): Princeton University engineers have developed power-generating rubber films that could be used to harness natural body movements such as breathing and walking to power pacemakers, mobile phones and other electronic devices. The material, composed of ceramic nanoribbons embedded onto silicone rubber sheets, generates electricity when flexed and converts mechanical energy to electrical energy. Shoes made of the material can harvest the pounding of walking and running to power mobile electrical devices.

Placed against the lungs, sheets of the material could use breathing motions to power pacemakers, obviating the current need for surgical replacement of the batteries which power the devices. The Princeton team is the first to successfully combine silicone and nanoribbons of lead zirconate titanate (PZT), a ceramic material that is piezoelectric, meaning it generates an electrical voltage when pressure is applied to it. Of all piezoelectric materials, PZT is the most efficient, able to convert 80 percent of the mechanical energy applied to it into electrical energy.

"PZT is 100 times more efficient than quartz, another piezoelectric material. You don't generate that much power from walking or breathing, so you want to harness it as efficiently as possible," said Michael McAlpine, a professor of mechanical and aerospace engineering, at Princeton, who led the project.

The researchers first fabricated PZT nanoribbons - strips so narrow that 100 fit side-by-side in a space of a millimeter. In a separate process, they embedded these ribbons into clear sheets of silicone rubber, creating what they call "piezo-rubber chips." Because the silicone is biocompatible, it is already used for cosmetic implants and medical devices.

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