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Walking could recharge your smartphone

Nanowires generate electricity through motion

Researchers at Georgia Institute of Technology are harvesting energy through activities like walking or running that could power or recharge smartphones and portable music players in the future.

Consumer electronics are quickly getting smaller, but the batteries cannot keep up, said Zhong Lin Wang, professor and director of the Center for Nanostructure Characterization at Georgia Institute of Technology. Smaller devices tend to consume less power, and the lab is trying to come up with ways in which motions like tapping, bending or walking could generate energy to keep the devices running.

The researchers have developed tiny nanowires made of zinc oxide that are capable of generating an electric field through force or motion. Zinc oxide has piezoelectric potential, which provides the ability for nanowires to convert mechanical energy into electric energy.

In lab tests, the researchers generated around 1.2 volts of energy just by tapping a substrate with 700 lines of nanowires. The electrodes connecting the rows of nanowires generated the electrical output.

"Any physical action that bends the substrate creates energy," Wang said. The electricity output also depends on the number of nanowires and the strength of the materials, said Wang, who is involved in the research.

More motion or mechanical pressure can generate additional energy, Wang said. For example, walking at a normal pace could generate 10 times more energy than tapping.

The researchers haven't performed actual field tests yet, but a future goal is to integrate the technology in music players and smartphones, Wang said. Within two to three years, the researchers hope to create substrates that are small and stable enough to implement to run low-power devices such as Bluetooth transmitters. In five years, the technology may be able to run and recharge mobile phones and portable music players as people walk or run.

The researchers have formed a company called Piezodyne to commercialise the technology.

Piezoelectric charges are already being used in devices like electromechanical sensors, energy converters and actuators, Wang said. The most popular piezoelectric material is PZT (lead, zirconia and titania), but it is not as ideal for consumer electronics, Wang said. Zinc oxide has qualities that adapt it better to consumer electronics, which could allow the creation of devices that fully operate through motion without the need for batteries, Wang said.

Many research efforts are also under way to harvest energy from other free energy resources. For example, Intel is working on tiny sensors that can capture energy from sources such as sunlight and body heat, which could power personal electronic devices such as cell phones for indefinite periods without recharging. Some devices such as watches are already available that are being powered by body heat.

See also:

MP3 player reviews

Smartphone reviews


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