Technology is steering toward miniaturisation in devices and components. With a growing demand for microscale and nanoscale technologies, there is a need for suitable power sources to overcome the limitations of conventional battery technology not being able to scale down to these levels.
Frost & Sullivan has noted that nanowires, which are structures exhibiting lateral dimensions constrained to nanometre scale, are gaining interest for the harvesting of mechanical energy to produce power. Researchers from the University of Illinois at Urbana-Champaign are studying these nanoscale systems that can harness energy from the environment to power nanoscale devices.
Due to their high length-to-width aspect ratios, nanowires exhibit different properties to bulk materials. The electrons in this case are quantum confined, thus occupying energy levels different from those found in the bulk material. This results in them exhibiting discrete values of electrical conductance arising from the constraint on the number of electrons travelling through a nanowire. This characteristic, along with scattering from wire boundaries and edge effects on electron motion, are some reasons for the lower conductivity of nanowires compared to the bulk material.
Nanowires made out of piezoelectric material generate a certain voltage under the effect of mechanical deformation. Researchers created the nanowire in the form of a single crystal of barium titanate, which is a common piezoelectric material. The most common technique to produce crystalline nanowires from semiconductor materials is vapour liquid solid synthesis.
Using laser abated particles or a feed gas as source material, catalyst exposure is performed to create crystalline nanowires. To test the performance characteristics of the nanowires, the researchers built very sensitive precision testing apparatus. The apparatus consists of a finger-sized device with two coplanar platforms exhibiting a displacement resolution of 1 nm range. The nanowire is placed in the gap between the two platforms and mechanical vibrations are induced on it. This results in a voltage being produced by the nanowires, which is measured by the precision sensing system.
The results indicate that the deformations in piezoelectric nanowires can be caused by sources other than external vibrations. The researchers are working on creating deformations in the nanowires by using acoustic waves.
Nanowires, which are primarily in the development stage, have promise to address applications such as nanoscale electronics and devices, quantum devices, biomolecular sensors and so on. The USA National Science Foundation funded the entire project with the research work being divided between the Centre for Microanalysis of Materials at the University and the US Department of Energy.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected]
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