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Ultrafine particle sensor that greatly improves air quality

Credits: Tim Staps

New methods for measuring the size and concentration of ultrafine particles using charged plasma can be used to create future sensors for health benefits.


Plasma is used in the manufacture of microchips, but it is also used in sensors that check for ultrafine particles that can pose a serious health risk. While such sensors are common in the industry, some issues such as cost, maintenance, and size need to be addressed before they can be used on a daily basis. In a study for his PhD, Tim Staps sought a new way to measure the size and concentration of particles in a plasma. It can be used in the future to create cheaper, smaller and more sustainable particle sensors. He defended his dissertation in the Department of Applied Physics on February 8.

Plasma, which is composed of charged particles and is one of the four states of matter, is a high-tech industrial system such as lithography machines that make microchips and ultrafine particle (UFP) sensors that measure the concentration of small particles (small particles). Used in. (0.1 micrometer or more) can be harmful to human health.

“For them Small sizeUFP can deposit deep into the lungs and enter the bloodstream, causing irreversible tissue damage and illness, “says Tim Staps, Ph.D. researcher, Ph.D. researcher, Complex Ionized Media Group, Department of Applied Physics. Says.

Sensor for society?

Industrial UFP sensors have been around for a long time, but there are some issues that must be overcome before they become commonplace in society. Rijksinstituut voor Volksgezondheid en Milieu (RIVM) estimates that inhalation of particulate matter (including ultrafine particles) released from automobiles and other processes will result in 7,000 to 12,000 deaths in the Netherlands. , Their availability is also timely. Per year.

The first problem is the cost, as the price of a laboratory-scale device is 10,000 euros, which is too high for a car. On the other hand, the widespread use of this technology is limited by the lack of legislation on ultrafine particles. However, many technical issues also prevent their widespread use.

“Not only does it create a compact UFP sensor, it doesn’t require ongoing maintenance. For example, industrial sensors need to be checked every 100 hours, which cannot be done in a car,” says Staps. .. “The UFP concentration in the air is low and difficult to measure, so the sensor must also be sensitive.”

“Accurate UFP sensors can protect people’s well-being by monitoring the indoor air quality of buildings and workplaces where UFP is common. Heating and ventilation to counter high concentrations of UFP. , Air conditioning can be introduced. Measure UFP and act on its detection. “

Ultrafine particle sensor that greatly improves air quality

Dust particles that scatter green laser light. Credits: Tim Staps

Surface charge measurement

In a study for his PhD, Staps and his colleagues developed a method to accurately measure the surface charge of annoscale particles. “First, we used the plasma to charge the particles by directing the electrons and ions of the plasma toward the particles, and then we measured the amount of charge carried by the particles. The total charge of all the particles, Measure the size and concentration of the particles. “

To measure the charge of a particle, Staps turned to microwave cavity resonance spectroscopy (MCRS). It has been used since the 1950s as a method for measuring free electrons in gas under vacuum conditions. However, in the new approach, Staps and his colleagues adopted this technique for use in normal conditions of pressure and air density.

“In a vacuum, electrons can travel many meters before colliding with gas or dust particles. Under normal conditions, this distance is significantly reduced and the electrons hit the gas or dust particles. When the signal is generated, it is much smaller than in a vacuum. We have designed a new setup that minimizes the effects of external vibrations and other signal noise sources. “

Under both vacuum and atmospheric conditions, Staps and researchers have found particles and Free electron It was determined whether the particles in the plasma were charged. “Such observations are important for understanding the physical process behind particle charging and discharging, but using the same data, a new theory explaining the charging process under variable pressure conditions. You can also develop. “

Detecting electron-particle collisions is one thing, but Staps and researchers then need to measure the electrons bound to the particles and the presence of negative ions (final dust particles) in the plasma. there was. However, in order to measure the charge, it is necessary to release the electron from the particle. To do this, researchers used a laser in combination with MCRS.

“The laser approach, known as photoelimination, shoots a large number of photons at the particle. Importantly, the photon energy exceeds the binding energy that traps the electrons on the particle surface, which is the charge on the particle surface. A truly unique way to detect. The presence of particles in vacuum and negative ions at atmospheric pressure. “

Ultra-fine detection in the field of view

So what does this all mean for ultrafine particle sensors? Now, Staps is very optimistic that his research may provide a good starting point for the development of future particle sensors.

“To create an accurate ultrafine particle sensor, we need to understand how small particles charge and use this data to develop a new theory of plasma-based charging of nanoparticles.” Staps said. “These insights could accelerate the advancement of sensor technology, and the production of these sensors on an industrial scale could happen sooner or later. However, the plasma interacting with the air is polluted very rapidly. There remains an engineering challenge of

In addition, accurate development sensor Can help the industry minimize production Ultrafine particles From the process, it improves air quality as a result and reduces the health risk of people working and living near the system that produces UFP.


Low temperature DeNOx catalyst to reduce ultrafine particle emission


For more information:
Toward the experimental characterization of nanoparticle charging in plasma. research.tue.nl/nl/publication… Particle charge-in

Quote: Ultrafine particle sensors (February 9, 2022) for significantly improving air quality can be found at https://phys.org/news/2022-02-ultrafine-particle-sensors-drastic-air.html. Acquired on February 9, 2022.

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Ultrafine particle sensor that greatly improves air quality

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