New Nanoscale Sensors Need No Power Source

Nanoscale sensors can be used for a wide variety of applications, in fields such as detecting dangerous molecules, or for sensing sounds in artificial ears. Their main drawback is the fact that they need to be integrated in larger devices, consisting of bulky power sources and integrated circuits, which considerably reduces their suitability for more uses. But that is all about to change, as researchers at the Georgia Institute of Technology (Georgia Tech) have recently demonstrated the first self-power nanosensor.

The nanoscale device can function on its own, and needn't be attached to external power sources, or other equipment. It is made entirely out of freestanding zinc-oxide nanowires that have the ability to generate electrical potential when placed under stress. This makes them behave in very much the same way transistors do, Technology Review reports. The research group that developed the new device was led by Georgia Tech Professor of Materials Science Zhong Lin Wang, who had conducted work on piezoelectric nanowires and nanogenerators before.

What the scientists basically get from the nanowires is a vertical field-effect transistor, with a diameter of just 25 nanometers. A part of the nanowires is embedded in a substrate, which has gold electrodes inside. These devices act as a source and a drain, enabling the production of electricity. When an external stimulus bends the zinc-oxide nanowire, all mechanical deformations are channeled to the embedded end of the wire, where electrical charges begin to build up. When the potential is high enough, it triggers a current flow from the source to the drain, acting like a gate voltage.

The new approach is groundbreaking, other researchers say. Previous studies concentrated on nanowires that were tethered at both ends. This severely limited their motion, and the electrical potential they were able to generate. The new setup is very similar to the way hair cells are positioned inside the ear. When sound waves move them, the electrical impulses they generate reach the brain via the auditory nerve, and are then transformed into the auditory sensation we perceive.

Wang's team is now looking to expand its discovery, and to produce arrays of the new devices, which, it says, could find applications in many fields. Still, some issues persist, the expert admits. The work “ is challenging because you have to make the electrical contact reliable, but we will be able to do that,” he concludes.