Structure formation of particles and micro droplets
In food, chemical and pharmaceutical industries, particle forming processes play a significant role. A typical example is the fluidized-bed coating. In this process a solid layer is formed, which protects solid nuclei from external influences such as light, moisture or oxidation. Moreover, such coating layers can also control the release rate of active ingredients from the coated nuclei. Simultaneously, properties of the product like flow-ability, stickiness and solubility can be adjusted and improved.
In order to create specific product and layer properties, an analysis of the micro-processes, which lead to the layer formation during the drying on the single particle, is required. A detailed investigation of the surface and the inside of coating is possible by using different offline measuring methods.
The confocal laser-scanning microscopy (CLSM) offers significant advantages compared to conventional microscopes and tomographic methods. The CLSM enables detailed views of the sample surface, using suitable dyes and fluorescent substances. By recording single layers of different sample depths a high resolution three-dimensional images of the surface coating can be reconstructed with high contrast.
CLSM records of sodium benzoate coating layer (left) and Shellac coating layer (right) on a glass core particle

For the investigation of the internal structure of the coating layer the X-ray micro-computed tomograph (µ-CT) is used. The particle, which is located at the optimum distance from the detector, turns on its own vertical axis. By recording single images a high-resoluted three-dimensional reconstruction is developed. Using image analysis, the components of the particle which need to be analyzed will be separated and evaluated.

Three-dimensional views of two different sodium benzoate coating layers

By means of Scanning Electron Microscopy (SEM) and White-Light-Interferometry (WLI) first information about the particle surface will be received. The WLI also measures the roughness of the surface.
With these measuring methods, it is possible to characterize single particles in detail.
SEM image of a Shellac coated particle     WLI reconstruction of a dried sodium benzoate droplet

In the framework of this study, the investigation of coated particles with the addition of fluorescent dyes will be compared with existing data from literature. Porous γ-alumina particles as well as compact glass beads are used as core materials. The coating materials which will be analyzed exhibit different properties. Mainly crystalline and amorphous materials with glass transition are investigated. The coating is applied in the top-spray fluidized bed process under a variety of process conditions.
Furthermore, colored micro-droplets are investigated by means CLSM in order to analyze the solid structure during and after the drying process. For this, droplets with different concentration of dye are generated with a microliter syringe and placed on flat glass or porous alumina oxide plate. The drying of these droplets is observed and evaluated with the confocal microscope.
Time series of a drying sodium benzoate droplet

The research project is funded by the German Federal Ministry of Science and Education (BMBF) as part of the InnoProfile-Transfer project "Unternehmen Region".


Dipl.-Ing. Franziska Sondej
University Course Drying 2020
30.03.2020 - 02.04.2020 in Magdeburg
University Course Fluidization Technology 2019
04.11.2019 - 07.11.2019 in Hamburg
Appreciation of the research work at the chair with title page of the journal Processes (MDPI)
First project meeting Wigratec InterSpiN
Award for Maciej Jaskulski
Cluster WIGRATEC enters the next round
Arun S. Mujumdar Medal for Prof. E. Tsotsas
Award for best oral presentation
Award for best oral presentation for Christoph Neugebauer on Population Balance Modeling Conference 2018
Faculty Prize 2018
Award for Prof. E. Tsotsas
Honorary Professorship of UCTM, Sofia, for Prof. Tsotsas
University Course Drying 2018
19. March -- 22. March 2018 in Magdeburg
University Course Fluidization Technology 2017
6. - 9. November 2017 in Hamburg
Award on Conference
Best Research Award for Sayali Zarekar on IDS in Gifu, Japan
Award on Conference
Best Poster Award for Christian Rieck at PARTEC 2016 in Nuremberg, Germany
Award on Conference
Best poster award for Vesselin Idakiev at national conference
Award on Conference
Best Presentation Awards on Nordic Baltic Drying Conference 2015
ECCE 2015
27. September - 01. October 2015 in Nice, France
Granulation Workshop 2015
1st July - 3rd July 2015 in Sheffield, UK
University Course Drying 2016
29. March -- 01. April 2016 in Magdeburg
Extension of the Research Training Group 1554
Extension of the funding period for 4.5 years
Award on annual conference
Award for best poster presentation goes to Maryam Dadkhah
Modern Drying Technology Vol. 3
Prof. E. Tsotsas in CES Top 20 Reviewer 2010
Award on Asia Pacific Drying Conference
VDI Ehrenring für Jun.-Prof. Mirko Peglow
University Course Drying 2014
Fundamentals and Applications of Drying Technology