Scientists create self-powered nanowire devices, potential to charge small electronics like cell phones                          by Aarti Kapoor

nanosensors

Georgia Tech professor Zhong Lin Wang holds an improved nanogenerator containing 700 rows of nanowire arrays. The generator was used to power nanometer-scale sensors. Photo: Gary Meek. Image source: Georgia Institute of Technology news release.

Atlanta, GEORGIA — Have you ever gone for a long walk, only to discover halfway through that your cell phone was flat and you needed to recharge it? 

Now, scientists at the Georgia Institute of Technology have created new and improved nano-sized power generators — small enough to be potentially used for charging cell phones, yet mighty enough to convert a light wind, ocean waves and even human physical motion into power capable of recharging an AA battery. 

Using a large number of zinc oxide nanowires to harvest the mechanical energy in the environment and generate sustainable electricity, the scientists produced self-powered sensors that can measure the pH value of liquids, and identify ultraviolet (UV) light, respectively. The study was published online March 28 in Nature Nanotechnology

Similar self-powered nanowire devices “can be used for powering small sensors, and charge small electronics such as cell phones,” according to Zhong Lin Wang, Regents’ professor in the School of Materials Science and Engineering at the Georgia Institute of Technology.

What’s more — since these zinc oxide nanowire devices rely on the environment for power, they will be able to work independently without requiring a battery.

“Zinc oxide is a cheap material and it can grow chemically at less than 100 degrees Celsius. It is biologically compatible and environmentally friendly,” Wang said.

Although the efficiency and durability of these zinc oxide nanowires have progressively improved over the years, the voltage and power produced by a single nanowire have been inadequate for actual devices. 

The challenge for Wang’s team was to integrate large numbers of nanowires into a single sustainable power source. They found that a lateral integration of 700 rows of zinc oxide nanowires produced a peak voltage of 1.26 volts at a low strain of 0.19 percent — potentially sufficient to recharge an AA battery. 

In another device, the team found that a vertical integration of three layers of zinc oxide nanowire arrays produced a peak power density of 2.7 milliwatts per cubic centimeter.

Wang’s team used the vertically integrated nanogenerator to power the nanowire pH sensor and the nanowire UV sensor mentioned above. Having successfully demonstrated these two nanowire-based, self-powered nanosensors, his team will continue to work in this area and create commercial products in the future.

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