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Researchers from university ETH Zurich have developed an ultra-sensitive temperature sensor from a bio-synthetic hybrid material of tobacco cells and nanotubes.
The sensor, which they say is at least 100 times more sensitive than existing sensors, works by changing its conductivity as the temperature changes.
Biologists have long-known that some plants are able to register fine differences in temperature by changing the conductivity of their cells in a process far more efficient than any man made sensor.
Raffaele Di Giacomo, a researcher in the project from the the department of Mechanical and Process Engineering at ETH Zurich, said: “We asked ourselves how we might transfer these cells into a lifeless, dry material in such a way that their temperature-sensitive properties are preserved.”
The cells were grown in a medium containing tiny tubes of carbon. These electrically conductive carbon nanotubes formed a network between the tobacco cells and were also able to penetrate the cell walls.
When Di Giacomo dried the nanotube-cultivated cells, he discovered a woody, firm material that he calls “cyberwood”. In contrast to wood, this material is electrically conductive thanks to the nanotubes, and with conductivity that is temperature-dependent and extremely sensitive, as it is in living tobacco cells.
Di Giacomo said: “No other sensor can respond to such small temperature fluctuations with such large changes in conductivity. Our sensor reacts with a responsiveness at least 100 times higher compared to the best existing sensors.”
Experiment have shown the cyberwood sensor can identify warm bodies at distance, such as a hand approaching the sensor from 36cm. The sensor’s conductivity depends directly on the hand’s distance from the sensor.
Further investigation also showed that pectins, which are molecules of sugar found in plant cells, play a key role in conductivity in plant cells and the cyberwood. As the temperature rises, the pectin breaks down and ions it contains move more freely and conduct electricity better.
The researchers have submitted a patent application for their sensor and are now aim to develop it so that it works without plant cells in a flexible, transparent and biocompatible sensor that can be moulded into shapes and produced at a low cost. Possible applications include biomedical devices, consumer electronics products and low cost thermal cameras.
[Picture shows cells form the tobacco plant used to build the by far most sensitive temperature sensor. (Illustration: Daniele Flo / ETH Zurich)]