Abstract
Microfluidic impedance flow cytometers enable high-throughput, non-invasive, and label-free detection of single-cells. Cytometers with coplanar electrodes are easy and cheap to fabricate, but are sensitive to positional differences of passing particles, owing to the inhomogeneous electric field. We present a novel particle height compensation method, which employs the dependence of measured electrical opacity on particle height. The measured electrical opacity correlates with the particle height as a result of the constant electrical double layer series capacitance of the electrodes. As an alternative to existing compensation methods, we use only two coplanar electrodes and multi-frequency analysis to determine the particle size of a mixture of 5, 6, and 7 µm polystyrene beads with an accuracy (CV) of 5.8%, 4.0%, and 2.9%, respectively. Additionally, we can predict the bead height with an accuracy of 1.5 µm (8% of channel height) using the measured opacity and we demonstrate its application in flow cytometry with yeast. The use of only two electrodes is of special interest for simplified, easy-to-use chips with a minimum amount of instrumentation and of limited size.
Highlights
We focus on electrical impedance flow cytometry
Electrical impedance flow cytometry offers non-invasive and label-free analysis of single cells in terms of size and dielectric properties, which enables a wide variety of biological cell studies [6,7,8,9], but loses some sensitivity and specificity compared with labeling techniques
Using our opacity-based alternative tive compensation strategy, we can adjust for the inhomogeneous electric field and detercompensation strategy, we can adjust for the inhomogeneous electric field and determine mine the particle size in an easy to fabricate coplanar setup with only two electrodes
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Planar electrodes have a higher sensitivity, but a complex fabrication process, whereas coplanar electrodes are less sensitive, but simpler and cheaper to fabricate [10,11] In both configurations, the position of particles is an important parameter for an accurate analysis of these passing particles or cells, as recently discussed by Daguerre et al [12]. Using our opacity-based alternative tive compensation strategy, we can adjust for the inhomogeneous electric field and detercompensation strategy, we can adjust for the inhomogeneous electric field and determine mine the particle size in an easy to fabricate coplanar setup with only two electrodes. Possible application in flowexperiment cytometry.with yeast cells [24,25,28] is performed to show its possible application in flow cytometry
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