Fabrication of a single nanodevice is no longer the state of the art in nanotechnology. The leading edge – and also currently the most challenging area in nanotechnology – is research that leads to a self-powered nanoscale system that is driven by the energy harvested from its environment and that can perform its work independently and sustainable. This is a key step toward self-powered nanotechnology, which is vitally important for medical science, environmental monitoring, defence technology and even personal electronics. Not to mention that it will lead to practically usable nanotechnology devices.
Each sensor is not required to work continuously and simultaneously, instead, it will have a 'blinking' working mode with a standby status and active status" says Wang. "The standby mode is normally longer, while the active mode is shorter. The energy scavenged and stored during the standby status can be used to drive it in the active mode. This means that these sensors periodically sample from their working environment and transmit data within a fraction of second. We can use the nanogenerator to harvest energy from the environment and store most of the energy when the sensor is in the standby mode. Then the collected energy will be used to trigger the sensor and then process and transmit the data in the active mode."
The nanogenerator fabricated by Wang's team is a free-standing cantilever beam that consists of a five-layer structure: a flexible polymer substrate; densely packed zinc oxide nanowire textured films on its top and bottom surfaces; and electrodes on the surfaces.
When it was strained to 0.12% at a strain rate of 3.56 % S-1, the measured output voltage reached 10 V, and the output current exceeded 0.6 µA (corresponding power density 10 mW/cm3).
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