Swisens Poleno FAQs

1What applications is Swisens Poleno useful for?
Swisens Poleno is used for longtime monitoring of particles in the air, like for example pollen or spores. It is the Swiss Army knife for aerosol research and helps to explore new particles but also to control particle formation for manufacturing processes.
2Which aerosol particle sizes does the Swisens Poleno measure?
Swisens Poleno measures PM1, PM2.5, PM10 and all particles up to 300µm in diameter.
3What information on aerosol particles do I get from Swisens Poleno?
Swisens Poleno provides the richest set of characteristics of every single particle on the market. Holographic images allow you to analyze volume, size and shape of every single particle. The fluorescence measurement setup provides further information about autofluorescence properties of each particle (fluorescence-intensity and -lifetime). Information about speed of particle and light polarization ratio complete the characteristic profile.
4How do you classify/identify the particles?
State-of-the-art machine learning algorithms process the rich set of characteristics from every single particle. The algorithms are able to differentiate between different particle classes / pollen types due to morphology and fluorescence properties.
5What is a two-step classification algorithm?
A two-step classification model means that we have 2 distinct steps in the way we identify particles that go through the instrument. The first step differentiates between pollen and non-pollen particles since the air contains a large number of aerosol particles from which only a small part is pollen. A large part are non-biological particles like ash, dust or water droplets (e.g. mist). The second step is then applied to just the pollen particles to identify the different taxa.
6How can I see what the system is actually measuring?
Every Swisens Poleno device comes with software and a database with REST API interface. The local database can be accessed via webbrower based user interfaces like the Swisens Data Explorer and provide information about the status and actual measurements.
7How do you train the system to identify a new particle type?
To train the device for a new particle type, a sample of this specific particle type is needed. This sample is then nebulized with our Swisens Atomizer into the air and measured by a Swisens Poleno device. Cleaning of the aquired dataset is then done by post-processing the data by classical image processing and clustering algorithms. An additional visual check of the holograpic images can be done it necessary.
8What are the differences between the Poleno air-flow cytometry system and other air-flow based systems?
The main difference between the Swisens Poleno and other air-flow cytometry systems is its use of inline holography imaging. To a certain extent, this allows a visual identification of the measured particles by human eyes which is valuable for the verification of the classification results from the algorithm.The Swisens Poleno also uses three different excitation wavelengths for the fluorescence measurement. This may enable a more precise evaluation of the fluorescence spectra of a particle and could help to determine more reliable fluorescence lifetime values. This, however, is still an area of research but the combination of imaging methods (holography) and fluorescence measurements for particle identification offer interesting perspectives for the future.
9Why do you use digital holography?
Digital holography as used in the Swisens Poleno essentially exploits the wave characteristics of light to make images of objects, without them needing to be in focus. A conventional camera needs the object to be in focus to be able to generate a sharp image of the object. However, this gets harder and harder the smaller and closer the objects are. Everyone who has used a microscope knows the difficulty to find the right focus plane. And even if you can find it, in most cases you only see one layer of it and the rest stays blurry. Imagine now, trying to make a picture with a microscope of a flying particle from which the distance is not exactly known and is traveling at 0.5 m/s (2km/h). This is really hard if not impossible. In contrast, holography makes it possible to refocus the image after it was taken. You can essentially sweep through to the whole measurement volume and search for the best picture. The prerequisite for this technique to work, however, is that the particle needs to be small and close to the image sensor, which is exactly the case when measuring pollen.
10What do I need to operate a Swisens Poleno?
For field operation, we recommend our complete Swisens Poleno monitoring station with an insulated weather protection housing. On site, there should be access to standard power mains. For roof installations, we recommend ground connection for lightning discharge and four rigging points. The whole monitoring station (incl. the device) weighs 130kg. The single device weighs 26kg.
11Can I operate multiple Swisens Polenos?
Swisens provides a simple solution for a central database, where local databases from deployed devcies can by synchronized to. This central database provides exactly the same interface like the local databases and is accessible via the same webbased user interfaces.
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