A View from Katherine Bourzac
Self-Powered Nanotechnology Closer to Reality
Researchers report a major boost in energy-harvesting devices.
This Tuesday at the Materials Research Society spring meeting in San Francisco I sat down with Zhong Lin Wang, director of the center for nanostructure characterization at Georgia Tech. We featured Wang’s work on self-powered nanosensors in our “10 Emerging Technologies” issue last year. The payoff from this concept would be huge: nanoscale sensors are exquisitely sensitive, very frugal with power, and, of course, tiny. They could be useful for detecting molecular signs of disease in the blood, minute amounts of poisonous gases in the air, and trace contaminants in food. Eliminating the batteries needed to drive these devices would make it possible to fully miniaturize them.
Wang has been developing devices based on nanowires that exhibit piezoelectricity. That is, they generate a voltage when they’re bent. He has been integrating these nanowires into devices that can harvest energy from biomechanical motion–including the running movements of a hamster on a wheel or the tapping of a finger–and use it to power a small sensor.
The problem with these devices has been getting a significant voltage out of them. This Tuesday morning, Wang presented recent data showing he has boosted the voltage produced by his nanowire devices by two orders of magnitude. The new design integrates millions of piezoelectric zinc-oxide nanowires in layered arrays on a plastic backing. Wang has coupled these devices with pH and UV-light sensors and demonstrated that they can power the sensor to take a measurement when stressed. Earlier this month, in the journal Nature, Wang reported a flexible device that produces 1.2 volts when it’s stressed; he says he has now made devices that produce 2.4 volts. This is enough to start thinking about integrating a charge-storage device that will make it possible to regulate the voltage going into the sensors for better control of measurements. Indeed, Wang says, that’s his next step.
Wang says he proposed the idea of self-powered nanotechnology based on these energy-harvesting devices in 2006, and at the time, there were many skeptics. Now others have started to replicate his results and other groups in academia and even at Samsung are starting their own research in the area.