A coplanar, low variation impedance flow cytometry design for characterization of bacteria

Electrical characterization of bacteria is becoming increasingly relevant in various scientific fields, with impedance flow cytometry (IFC) emerging as a powerful label-free technique. However, coplanar electrode configurations suffer from a key limitation: the signal depends on the particle position above the electrodes, which can make differentiation of particles unreliable. This thesis investigates strategies to minimize the positional dependence of the signal through finite element method simulations in COMSOL. Several electrode layouts are explored and asymmetric gaps are found to introduce signal features that correlate with particle position in the channel. Two parameters related to width and amplitude of peaks in the characteristic IFC signal are identified as potential indicators of vertical position. An experimental setup including a 3D-printed holder for the chip and a 3D-printed framework for the alignment of electrodes in the channel is developed to experimentally validate the simulation results. Measurements on polystyrene beads show trends consistent with simulations, supporting the feasibility of a compensation strategy for the positional dependence of the signal based on the extracted parameters. While a full compensation model is not achieved here and tests with biological samples are yet to be performed, this study establishes a promising foundation for further research and future improvements in the performance of IFC systems using coplanar electrode configurations.