Particle measurement: “Singing” sensors against air pollution

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Fine particulate air pollution in cities throughout Europe is to be reduced. But to do this, the local authorities need sufficiently accurate and inexpensive measuring methods. A new sensor technology could solve the problem in the future.

The EU Commissioner for the Environment is becoming increasingly concerned about the quality of the air that Europeans breathe. Because of this, he is urgently demanding that measures to improve air quality are accelerated. However, this requires a dense network of measuring stations with the right measurement methods. At present, to assess fine particulates, many of these stations use the weight of the particles, which is, however, very dependent on their moisture content and provides little information about actual toxicity. The results also deviate considerably in many cases. But among other things, real-time measurement of actual vehicle emissions is needed to introduce effective emission reduction measures in cities.

Within the scope of the Horizon 2020 research project CARES (City Air Remote Emission Sensing), an international research consortium – including scientists from Graz University of Technology, Austria, and Heidelberg University, Germany – are working on contactless exhaust measuring methods. In the future, stations installed at the side of the road, on crash barriers, or on traffic signs, containing innovative sensors will measure the emissions of passing vehicles in a matter of seconds without affecting the flow of traffic.

For example, this would allow the exhaust gas class of each individual vehicle to be measured simply and inexpensively. This, in turn, could be used as a basis for an emissions-based city toll, which “punishes” higher exhaust values with a higher charge. It would also allow monitoring of entry permits to environmental zones. Barriers would then open automatically for approaching vehicles with exhaust emissions within the accepted range. The sensors would also be able to identify vehicles in which the engine performance and, consequently, exhaust emissions had been increased through manipulated particle filters or chip tuning.

Particle measurement with tuning forks

The inexpensive remote emission measurement sensors should be ready for serial production when the project ends in 2022. Initial promising tests at the institute in Graz work with conventional tuning forks that are excited with laser pulses. The particles between the tines of the fork produce an acoustic signal and begin to “sing” in the truest sense of the word. Each individual particle emits acoustic signals, which are recorded and played back by the tuning fork. The more particles there are, the louder the sound becomes.

The technology is already being used successfully for gas measurements. The scientists in Graz were able to show for the first time that this also works with particles and could be a possibility for a low-cost sensor.

About the project

The CARES research project is funded within the Horizon 2020 Research and Innovation Program of the European Union with EUR 3,326,735.50 and is anchored in the “Information, Communication & Computing” Field of Expertise, one of five strategic focal areas of Graz University of Technology.

 

 

 

 

Particle measurement (Image: TU Graz).

Tuning forks to reduce fine particulate air pollution in European cities. (Image: TU Graz).