ZnO nanowires with reduced diameters could make ideal building blocks for self-powered nanodevices thanks to their piezoelectric properties. We used density functional theory (DFT) calculations in conjunction with maximally localized Wannier functions (MLWFs) to study the piezoelectric properties of ZnO NWs with diameters smaller than 2.3 nm. Using this scheme, we were able to quantify both bulk and surface contributions. The close similarity between piezoelectric responses of bulk and nanostructure NWs reveals that piezoelectric constants are not enhanced at the nanoscale. This finding is different from previous observations.

On the contrary, the calculated effective strain energies of ZnO NWs are more sensitive to smaller nanowire size and are much lower compared to the bulk material. As such, our theoretical predictions indicate that the advantage of using NWs for energy harvesting comes thanks to their sensitivity to small mechanical agitation, thus making them ideal candidates for building efficient energy scavenging devices - irrespective of the fact that NW nanogenerators (which are typically around 40 nm in size) are expected to have piezoelectric properties similar to bulk ones.

More information can be found in the journal Nanotechnology (in press).

Further reading

Piezoelectric nanowires power up under load (Oct 2007)
Nanofibres power portable electronics (Jul 2010)
Structural monitoring added to application list for nanogenerators (Feb 2013)