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Sensors target water, air pollutant detection

29 May 2013

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Sensors that can detect water and air pollutants in situ and in real-time are being developed by researchers from the University of Delaware (UD) in the US.

Juejun Hu and Chaoying Ni of UD's Department of Materials Science and Engineering are creating small, highly sensitive devices that will detect organic, inorganic and biological molecular species at low levels in the environment.

With further research and development, the devices could be integrated into portable, battery-powered sensor packages, replacing more traditional molecular detectors, which require bulky and expensive equipment.

Deployed in a network in the field, an array of the small sensors could detect contamination in air, water and soil in real time and relay that information wirelessly to a computer.

A major obstacle preventing small sensors from becoming practical replacements for bulky machines is that the new technology is still less sensitive and specific in its detection than the instruments currently in use. The project aims to create sensors that overcome these obstacles.


Optical absorption signals are key

The researchers use a focused ion beam (FIB) to punch holes into a thin strip of chalcogenide glass (ChG) a few micrometres thick, or about one-tenth the width of a hair. When light passes through the strip, molecules in the environment selectively absorb one or a few particular colours of the light. The unique optical absorption signals can then be used to identify the presence and concentration of the molecules of interest. The researchers plan to group several of the tiny, chip-sized devices together to create a sensor capable of detecting multiple types of molecules.

"In the end, the device will be very sensitive compared to current technology. We expect around two to four orders of magnitude improvement," said Hu. "It will also be small and leave a very small footprint. Once integrated, it will be the size of a hockey puck and can be placed discreetly in the environment."

Although the project is still in its early stages, with testing only starting recently, Hu is already looking ahead to the practical benefits the devices could have for the environment.

"We'll be able to continuously monitor environmental pollutants, so we'll know if water in a stream is getting polluted or if a chemical plant is leaking. We can also use it to detect toxic leaks in industrial plants," he said.

Hu added that once the technology is sensitive enough, chip-scale sensors could be useful in other fields, including biomedicine.

"We could use the devices to check for certain diseases by analysing a patient's breath," he said. "The sensor would be able to detect trace molecules in the air they exhale."


Watch a short video about the study below:





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