Cavadini P., Weinhold H., Tonsmann M., Chilingaryan S., Kopmann A., Lewkowicz A., Miao C., Scharfer P., Schabel W.

in Experiments in Fluids, 59 (2018), 61. DOI:10.1007/s00348-017-2482-z


© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. To understand the effects of inhomogeneous drying on the quality of polymer coatings, an experimental setup to resolve the occurring flow field throughout the drying film has been developed. Deconvolution microscopy is used to analyze the flow field in 3D and time. Since the dimension of the spatial component in the direction of the line-of-sight is limited compared to the lateral components, a multi-focal approach is used. Here, the beam of light is equally distributed on up to five cameras using cubic beam splitters. Adding a meniscus lens between each pair of camera and beam splitter and setting different distances between each camera and its meniscus lens creates multi-focality and allows one to increase the depth of the observed volume. Resolving the spatial component in the line-of-sight direction is based on analyzing the point spread function. The analysis of the PSF is computational expensive and introduces a high complexity compared to traditional particle image velocimetry approaches. A new algorithm tailored to the parallel computing architecture of recent graphics processing units has been developed. The algorithm is able to process typical images in less than a second and has further potential to realize online analysis in the future. As a prove of principle, the flow fields occurring in thin polymer solutions drying at ambient conditions and at boundary conditions that force inhomogeneous drying are presented.

Lewkowicz, Alexander

Internship report, Institute for Data Processing and Electronics, Karlsruhe Institute of Technology, 2014.


High speed tracking of fluorescent nano particles enables scientists to study the drying process of fluids. A better understanding of this drying process will help develop new techniques to obtain homogeneous surfaces. Images are recorded via CMOS cameras to observe the particle flow. The challenge is to find particles 3rd coordinate from a 2D image. Depending on the distance to the objective lens of the microscope, rings of different radii appear in the images. By detecting the rings radii and coordinates, both velocity and 3D trajectories can be established for each particle. To achieve almost real-time particle tracking, highly parallel systems, such as GPUs, are used.

Supervised by  Dr. Suren Chilingaryan