Extraction of Material Properties for Optimised Acoustophoresis-Based Particle and Cell Separation Using Flow Cytometry Data

Sammanfattning

Acoustophoresis enables label-free separation of particles and cells in microfluidic sys- tems, but systematic methods for analysing and comparing separation behaviour re- main limited. In this thesis, a workflow based on the mobility ratio was evaluated as an experimental framework for characterising acoustophoretic separations, using flow cytometry as the analytical tool. Separation experiments were performed on polystyrene beads and human cell lines (K562 and Jurkat) under varying separation voltages and buffer conditions. Sepa- ration quality was quantified using flow cytometry, and mobility ratios were experi- mentally derived from the voltages corresponding to equal outlet splitting (SQ50) of the separated particles and cells. For polystyrene beads, the measured mobility ratios showed good agreement with the- oretical expectations based on particle size, demonstrating robustness of the SQ50- method. The experiments with cells exhibited increased variability, both in the mea- sured and expected values, reflecting the heterogeneity of biological samples. While the measured mobility ranges were within the expected range, the SQ50-points showed greater variation between runs compared to polystyrene beads. This indicates that the method is less robust for cells, however it can still be applied. Addition of 15% iodix- anol did not greatly affect the acoustic behaviour of K562 and Jurkat cells. Separation of K562 and Jurkat cells resulted in mobility ratios close to unity, consistent with their similar acoustic properties and overlapping size distributions. Together, these findings demonstrate that the mobility ratio is a robust and exper- imentally accessible parameter for characterising acoustophoretic separations, while also clarifying its limits for biological samples.