Nanogenerators that stand the test of time
Juin 23, 2017 Dr Richard Collins
Earlier this month, IDTechEx analysts were invited to attend the second talk within the "From Discovery Science to Industrial Application" series, co-organised by the Cambridge Network and the Maxwell Centre. These talks aim to highlight some of the leading research carried out at the University of Cambridge, which has long-term commercial opportunities. On this occasion, Dr Sohini Kar-Narayan gave the talk on Nanogenerators for energy harvesting applications.
Dr Kar-Narayan and her research team have been working on the increasingly popular nanogenerators as energy harvesters, which spawned as a research topic from the work of Professor Wang at Georgia Tech, US. Kar-Narayan's group took an alternative initial approach, looking to solve the limited lifespan that the classic ZnO nanogenerators have faced due to surface degradation.
The early success came by the way of growing and embedding these forests of ZnO fibres in a nanoporous template, such as a polycarbonate polymer. This removed the atmospheric exposure, which maintained the performance of this nanogenerator for 9-months. What's more, with an eye always towards eventual commercial success, the wetting technique employed for the synthesis proved easy and scalable.
The same templating technique was turned to other materials and more recently somewhat overlooked polymer-based piezoelectric materials, proved another great success. Anodized aluminum oxide was used as the template and nylon-11 nanowires grown. Not only did the template protect the nylon-11 to degradation on atmospheric exposure, but a higher crystallinity was achieved resulting in a "self-poled" material with a higher piezoelectric coefficient.
The headline performance from their 2017 paper in Advanced Functional Material was the production of "an open-circuit voltage of 1 V and short-circuit current of 100 nA, when subjected to small amplitude, low frequency vibrations".
Piezoelectric polymer nanowires grown by template-wetting. Source: http://people.ds.cam.ac.uk/sk568/campl_site/index.shtml
The form of energy harvesting discussed was not just limited to vibrational sources, but extended to the new hot-topic of triboelectricity. The polymeric materials lend itself nicely to these pursuits with nylon sitting in the positive spectrum of the triboelectric series. These are in the early stages of investigation and operate with both a sliding or tapping motion and a range of counter materials. Dr Kar-Narayan stated that there are many more materials that are being explored for these nanogenerators and that there is a great potential looking forward.
IDTechEx note that the nanogenerators are still waiting to come out of the lab and onto the commercial stage, but the applications in an ever-increasingly connected world of efficient low-power IoT nodes make the opportunities all the greater when they do.
To learn more about the trends, commercial landscape and main players see IDTechEx research at www.IDTechEx.com/research/eh. In addition, the largest exhibition on energy harvesting will be held at the IDTechEx Show! in Santa Clara, US, from 15-16 Nov. Find out more at www.IDTechEx.com/usa.
For more information on the Maxwell Centre visit www.maxwell.cam.ac.uk.