Nano-electricity by harvesting mechanical energy from the environment

Researchers at the University of Illinois have shown in a new study that a single nanowire can produce power by harvesting mechanical energy.

Washington, Sept 28 : Researchers at the University of Illinois have shown in a new study that a single nanowire can produce power by harvesting mechanical energy.

Made of piezoelectric material, the nanowire generates a voltage when mechanically deformed. To measure the voltage produced by such a tiny wire, however, the scientists first had to build an extremely sensitive and precise mechanical testing stage.

"With the development of this precision testing apparatus, we successfully demonstrated the first controlled measurement of voltage generation from an individual nanowire," said Min-Feng Yu, a professor of mechanical science and engineering, and a researcher at the university's Beckman Institute.

"The new testing apparatus makes possible other difficult, but important, measurements, as well," Prof. Yu said.

The team of Prof. Yu and graduate students Zhaoyu Wang, Jie Hu, Abhijit Suryavanshi and Kyungsuk Yum, first synthesized the nanowires in the form of a single crystal of barium titanate, an oxide of barium and titanium used as a piezoelectric material in microphones and transducers.

The precision tensile mechanical testing stage is a finger-size device consisting of two coplanar platforms - one movable and one stationary - separated by a 3-micron gap.

The movable platform is driven by a single-axis piezoelectric flexure stage with a displacement resolution better than 1 nanometer.

When the researchers' piezoelectric nanowire was placed across the gap and fastened to the two platforms, the movable platform induced mechanical vibrations in the nanowire. The voltage generated by the nanowire was recorded by high-sensitivity, charge-sensing electronics.

"The electrical energy produced by the nanowire for each vibrational cycle was 0.3 attojoules (less than one quintillionth of a joule). Accurate measurements this small could not be made on nanowires before," said Prof. Yu.

Prof. Yu said while the team was able to successfully create mechanical deformations in the nanowire through vibrations caused by external motion, other vibrations in the environment, such as sound waves, should also induce deformations.

The team's next step is to accurately measure the piezoelectric nanowire's response to those acoustic vibrations, Prof. Yu said.

The research appears in a paper due for publication in the journal Nano Letters.

ANI