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BP: Fachverband Biologische Physik

BP 17: Poster Session II

BP 17.36: Poster

Dienstag, 18. März 2025, 18:00–20:30, P4

Characterizing diffusion properties at liquid-liquid interfaces in microfluidic channels — •Eric Schneider, Eric Sündermann, Bob Fregin, and Oliver Otto — Institute of Physics, University of Greifswald, Greifswald, Germany

Real-time deformability cytometry is a powerful and widely used method for investigating the mechanical properties of cells in suspension. Here, cells are deformed by hydrodynamic stress in a microfluidic system, that is comparable in size to the cells. Consequently, the range of cell sizes has to match the physical channel dimensions to ensure proper cell deformation. Virtual fluidic channels (VFCs) address this limitation, by allowing for the channel width to be adjusted within seconds. VFCs are formed by the liquid-liquid interface between two co-moving aqueous polymer solutions. The introduction of these two different polymer solutions generates a density gradient within the microfluidic channel, which can give rise to diffusive processes. We investigated the diffusive properties within VFCs and the influence of the liquid-liquid interface. For this, we examined the temporal behavior of a fluorescent dye distribution within the microfluidic chip. We modelled the diffusive behavior self-consistently by solving the kinetic diffusion equation, which accounts for the differential flow velocities within the microfluidic channel. Finally, by combining theoretical and experimental results, we determine the characteristic diffusion timescales in the VFC and across the liquid-liquid interface. With this we provide a general framework to investigate the diffusive properties along laminar flow boundaries.

Keywords: Diffusion; Laminar flow; Deformability cytometry; Kinetic equations