Scientists build miniscule solar cells to power microscopic machines

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Washington, Nov 7 : Scientists have successfully tested the tiniest solar cells ever built, which can act as a power source for even tinier microscopic machines for detecting dangerous chemicals and toxins.

In a new study, scientists have shed light on an inch-long array of 20 of these cells, each one about a quarter the size of a lowercase "o" in a standard 12-point font. Xiaomei Jiang, who led the study at the University of South Florida, said that the cells were made of an organic polymer and were joined together in an experiment aimed at proving their ability to power tiny devices that can be used to detect chemical leaks and for other applications

Solar cells of the traditional variety, like those installed on rooftops, use a brittle backing made of silicon, the same sort of material upon which computer chips are built.

On the other hand, organic solar cells rely upon a polymer that has the same electrical properties of silicon wafers but can be dissolved and printed onto flexible material. "I think these materials have a lot more potential than traditional silicon. They could be sprayed on any surface that is exposed to sunlight -- a uniform, a car, a house," said Jiang.

The researchers created their array of 20 tiny solar cells as a power source for running a microscopic sensor for detecting dangerous chemicals and toxins.

Called a microelectromechanical system (MEMS) device, the detector is built with carbon nanotubes and has already been tested using ordinary DC power supplied by batteries. After the carbon nanotubes are fully powered and hooked into a circuit, they can sensitively detect particular chemicals by measuring the electrical changes that occur when chemicals enter the tubes.

It is possible to detect the type of chemical by observing the exact change in the electrical signal.

The device needs a 15-volt power source to work, so far and Jiang's solar cell array can provide about half of that -- up to 7.8 volts in their laboratory tests.

She claims that they are now planning to optimize the device to increase the voltage and then combine the miniature solar array to the carbon nanotube chemical sensors.

Jiang estimated that they would be able to demonstrate this level of power with their next generation solar array by the end of the year.

The findings of the study are published in the inaugural issue of the Journal of Renewable and Sustainable Energy (JRSE).

ANI

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