Performance-enhanced clogging-free viscous sheath constriction impedance flow cytometry

As a label-free and high-throughput single cell analysis platform, impedance flow cytometry (IFC) suffers from clogging caused by a narrow microchannel as mechanical constriction (MC). Current sheath constriction (SC) solutions lack systematic evaluation of the performance and proper guidelines for the sheath fluid. Herein, we hypothesize that the viscosity of the non-conductive liquid is the key to the performance of SC, and propose to employ non-conductive viscous sheath flow in SC to unlock the tradeoff between sensitivity and throughput, while ensuring measurement accuracy. By placing MC and SC in series in the same microfluidic chip, we established an evaluation platform to prove the hypothesis. Through modeling analysis and experiments, we confirmed the accuracy (error < 1.60% +/- 4.71%) of SC w.r.t. MC, and demonstrated that viscous non-conductive PEG solution achieved an improved sensitivity (7.92x) and signal-to-noise ratio (1.42x) in impedance measurement, with the accuracy maintained and free of clogging. Viscous SC IFC also shows satisfactory ability to distinguish different types of cancer cells and different subtypes of human breast cancer cells. It is envisioned that viscous SC IFC paves the way for IFC to be really usable in practice with clogging-free, accurate, and sensitive performance.

Automated summary

As a label-free and high-throughput single cell analysis platform, impedance flow cytometry (IFC) can suffer from clogging issues. This study proposes the use of non-conductive viscous sheath flow in current sheath constriction (SC) solutions to improve sensitivity and throughput while maintaining accuracy. By placing mechanical constriction (MC) and SC in series in the same microfluidic chip, the hypothesis is proven through modeling analysis and experiments. The results show that viscous non-conductive PEG solution improves sensitivity and signal-to-noise ratio in impedance measurement, without clogging, while also demonstrating the ability to distinguish different types of cancer cells and subtypes of human breast cancer cells.