Nanogenerators: The Cleverest Things You’ve Never Seen

Incredible advances in nanotechnology, including biomedical and wearable electronics, require innovations in suitable power sources. Nanogenerator technology is surging forward to meet this need.

What are Nanogenerators

The word nano means billionth, so a nanometer is one billionth of a meter. This is the tiny world in which nanogenerators operate, visible only through high-powered microscopes. Generating power at this scale requires specialized methods of energy harvesting. The three types of nanogenerators currently in development by researchers around the world are piezoelectric, triboelectric, and pyroelectric. So how do these tiny marvels work?

Piezoelectric Nanogenerators

[Image source: Wikimedia]

Piezoelectric nanogenerators utilize the piezoelectric effect to generate electricity. From the Greek word piezein, meaning press, the piezoelectric effect describes the creation of an electrical field in response to deformation of the crystalline structure of the material. This occurs due to the change in relative position of polarized molecules within the structure. Deformation may occur by the application of direct pressure or through vibration.

Triboelectric Nanogenerators

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The triboelectric effect governs the operation of triboelectric nanogenerators. From another Greek word tribo, meaning rub, the triboelectric effect is the phenomenon by which electrons are transferred from one material to another through contact, creating a difference in electric potential between the two surfaces.

Pyroelectric Nanogenerators

As you’d expect, pyroelectric nanogenerators utilize – you guessed it – the pyroelectric effect. This effect describes the generation of a voltage via a heat differential. Voltage generation occurs within certain materials when they are heated, due to small positional changes of polarized atoms within the structure.

Anatomy of a Nanogenerator

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The selection of materials that make up a nanogenerator depends upon its method of energy collection. A leading group of researchers in nanogenerator technology works out of the Georgia Institute of Technology. This team, led by Professor Zhong Lin Wang, are focusing their efforts on piezoelectric nanogenerators, using Zinc Oxide (ZnO) nanowires.

Another research team has taken a different approach to piezoelectricity generation at a nano-scale. Their material of choice is lead zirconate titanate (PZT). This material is extremely brittle, however, a problematic property for a material under strain. The team have come up with a unique way to get around this, forming the PZT into nanoribbons and setting them out in a wave-like pattern.

Applications

From sensors to wearable electronics, the range of available nanotechnologies is growing every year. Incredible innovations in biomedicine in recent years are reminiscent of our science fiction dreams of the 1980s. Implantable medical devices require constant, reliable power, and invasive surgery to replace battery packs is a less than perfect solution. The automatic movements of the body, including the heart beat and breathing, could provide the kinetic energy required by piezoelectric nanogenerators. The tiniest of movements produce friction, with the potential to power triboelectric nanogenerators. Waste heat energy abounds in the human body, providing fuel for pyroelectric nanogenerators.

[Image source: Wikimedia]

2012 saw some massive advances in output power density of nanogenerators and the growing number of researchers around the world show no sign of slowing this progress. From technology embedded in your clothes to under-skin implants, nanogenerators promise to make the future of nanotechnology far more user-friendly.

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