Extensional-Flow Impedance Cytometer for Contactless and Optics-Free Erythrocyte Deformability Analysis

Objective: Deformability is an essential feature of red blood cells (RBCs), enabling them to undergo significant shape change in response to external forces. Impaired erythrocyte deformability is associated with several pathologic conditions, and quantitative measurement of RBC deformability is critical to understanding and diagnosing RBC related diseases. Whereas traditional approaches to cell mechanical characterization generally have limited throughput, emerging microscale technologies are opening new opportunities for high-throughput deformability cytometry at the single-cell level. Methods: In this work, we propose an innovative microfluidic system based on (i) a hyperbolic microchannel to induce erythrocyte deformation by extensional flow, and (ii) an electrical sensing zone with coplanar electrodes to evaluate the deformed cell shape. Results: RBC deformation under extensional flow is achieved, and the deformed cell shape is quantified by means of an electrical anisotropy index, at a throughput of 300 cell/s. Measurements of healthy and chemically stiffened RBCs demonstrate that the anisotropy index can be used to characterize RBC deformability, as an alternative to deformation indices based on high-speed image processing. Conclusion: A contactless and optics-free approach for RBC deformability analysis has been presented. Significance: Due to its simplicity and potential for integration, the proposed approach holds promises for fast and low-cost erythrocyte deformability assays, especially in point-of-care and resource-limited settings.