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A Step Ahead For Zinc Oxide Piezoelectrics: Over 20 Times Power Improvement


Piezoelectrics are a class of materials that, if applied a mechanical force, exert an electric current on the sides. You may already have knowledge about this, but researchers are studying how to take piezoelectric materials to the next step.

Specifically, they want to embed these devices in flexible materials, so that clothes, for example, can produce enough electricity to power small appliances (MP3s, phones, etc).

The director of Georgia Tech’s Center for Nanostructure Characterization, Zhong Lin Wang, and a team of other Georgia Tech researchers, have developed nanowire-based generators for the first time. Moreover, their discoveries constitute a giant leap forward since the devices they developed can actually power LCD displays and LEDs.

Back in 2005, Wang was the first to demonstrate that nanoscale piezoelectric devices can exist, but the first prototypes could hardly power anything. Since then, Wang and his team produced a nanogenerator that contained more nanowires over a large area (1.5×2 centimeters) that produced two volts, enough to power a calculator LCD. “We were generating 50 millivolts in the past, so this is an enhancement of about 20 times,” says Wang.

Their piezoelectric device was made by dripping a solution containing zinc oxide nanowires onto a thin metal electrode sitting on a sheet of plastic, creating several layers of the wires. They then covered the material with a polymer and topped it with an electrode.

A pacemaker requires 5 milliwatts and an iPod 80 milliwatts, so the 11-mW per cubic centimeter developed by Wang is pretty close to meeting everyday needs.

The researchers now study how to make nanowire PZT material. PZT is a crystalline material that contains lead, zirconium and titanium, and is the best piezoelectric material known. Still, making it into nanowires requires a good catalyst and they haven’t found it yet.

Instead, they used another solution, by treating the starting solution at high temperatures and pressures, which eliminates the need for a catalyst. This way they create a flat thin film of nanowires, which they then chemically etched using a nanowire pattern.

Having just begun working with PZTs, the researchers hope for the best, though they are still not obtaining the same results as they do with the previously-invented zinc oxide material.

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