New ways to confine, control, and measure harmful dust particles

Soot and smog, which are both examples of particulate matter air pollution, consist of harmful dust particles that float through the atmosphere. The presence of both significantly reduces air quality.

More specifically, ultrafine dust particles, which have a size smaller than 100 nanometers, can infiltrate the respiratory system and even enter the vascular system. Once inside, they pose a risk to the entire human body, and studies have demonstrated that these particles increase the risk of various respiratory diseases.

The field of research into particulate air pollution is still relatively young, but global health organizations recently established air quality and particular matter pollution as one of the focus points. As a result, air quality monitoring platforms are raised globally and dust sensors are implemented in devices suitable for daily use, such as cars and vacuum cleaners.

Confine and measure

The accurate quantification of air pollution is a major technical challenge that must be overcome. Thorough measurement of air pollution is important when it comes to monitoring and controlling air pollution associated with ultrafine dust.

For his cum laude PhD research, Tim Donders looked at two main aspects of the problem. First, he looked at methods to generate, confine, and control nanometer-sized solid contamination in a gaseous environment. This could then be used to calibrate existing sensors used to monitor dust particles. Second, he developed new, minimally invasive techniques for measuring the size of these dust particles.

Nanodusty plasmas

For the research, Donders and his colleagues proposed the use of a nanodusty plasma as a suitable environment for the generation of ultrafine dust particles in a gaseous environment.

A plasma is defined as a partially ionized gas, containing neutral atoms, free electrons, and both positive and negative ions. When igniting a plasma in a gas mixture containing a reactive precursor gas, a cloud of nanometer-sized solid dust particles can be formed and confined. In this way, dust particles can be grown relatively monodisperse in size, which makes the system also suitable for the development of new diagnostic techniques.

New insights

All in all, the work in Donders’ thesis describes several new insights into dust particle behavior and charging in a nanodusty plasma.

He developed an experimental setup in which ultrafine dust can be grown, confined, and monitored in a highly controlled way, and developed two novel techniques to measure one of the key properties of ultrafine dust particles.

The detection limit of both methods is well below 100 nanometers, which makes them near or even below the detection limits of currently available particle sizing methods.

In this way, the methods offer a proper calibration method for ultrafine particle sensors and may eventually contribute to quantifying and regulating atmospheric air pollution, with the goal of increasing the quality of the air we breathe every day.

Title of PhD thesis: Characterization and diagnostics of dust growth in nanodusty plasmas. Supervisors: Job Beckers and Gerrit Kroesen.