An engineering research team from the Columbia University and the Georgia Institute of Technology (Georgia Tech) have developed the smallest and thinnest electric generator of all time: it measures 5 x 10 microns (one micro is one millionth of a metre). The development, based on the phenomenon of piezoelectricity, opens up possibilities for new types of mechanically controlled electronic devices.
Piezoelectricity is a well-known phenomenon among scientists: when a material stretches or compresses, it creates an electric voltage. Similarly, when a voltage is applied, the material expands or contracts. However, the phenomenon had not been observed before in materials with a low atomic thickness; it had only been predicted theoretically.
The research team from the abovementioned institutions have observed and demonstrated piezoelectricity or the mechanical generation of electricity in an atomically thin material called molybdenum disulfide (MoS2). Although it is not piezoelectric in its bulk form, it acquires this property when it is reduced to a single atomic layer. In other words, it is a naturally occurring three-dimensional material called molybdenite, which is not capable of generating electricity even when mechanical pressure is applied. This capacity is only acquired when it is reduced to two dimensions (MoS2).
Image: the Georgia Tech researchers Wenzhuo Wu and Zhong Lin Wang. Author: Rob Felt.
Consequently, they have managed to create an optically transparent, extremely light and flexible nanogenerator, which can be stretched. An article about the project was published on 15th October in the magazine Nature.
The scientists studying the properties of materials are very excited about molybdenum disulfide. James Hone, professor of Mechanical Engineering at Columbia and co-leader of the research team, says, “We’re eager to build useful devices for all kinds of applications.” He adds, “This material – just a single layer of atoms – could be made as a wearable device, perhaps integrated into clothing, to convert energy from your body movement to electricity and power wearable sensors or medical devices, or perhaps supply enough energy to charge your cell phone in your pocket.”
“This is the first experimental work in this area and is an elegant example of how the world becomes different when the size of material shrinks to the scale of a single atom,” Hone explains. For now, the energy produced by these micro generators is very limited, but the researchers are already working on how to increase it.
