On‐Chip Evaluation of Red Blood Cell Deformability Through Transit Velocity Index in Hematological Diseases

ABSTRACT This study introduces a novel method for evaluating red blood cell (RBC) deformability using a microfluidic platform equipped with constriction channels that mimic capillary vessels. The normalized transit velocity of RBCs at 50% compression ratio (V^ _{ε = 0.5} ) is proposed as a quantitative index of RBC deformability. Experimental validation is conducted in two key phases. First, to validate the proposed index, a controlled reduction in RBC deformability is induced using varying concentrations of diamide. V^ _{ε = 0.5} progressively decrease as the diamide concentration increased, confirming that the index tracks changes in RBC deformability. Second, to demonstrate the ability of the platform to detect disease‐specific properties, RBCs from patients with iron deficiency anemia (IDA), thalassemia (Thal), and hereditary spherocytosis (HS) are analyzed. The results reveal elevated deformability from IDA and Thal patients, and reduced deformability from HS patients. High V^ _{ε = 0.5} values consistently correlate with RBC characteristics known to enhance deformability—such as thin, elliptical morphology, a high surface‐area‐to‐volume ratio, and low internal viscosity—whereas lower values are associated with characteristics that impair deformability. These findings highlight the impact of RBC characteristics on deformability and the importance of our microfluidic platform as a robust tool for investigating hematological diseases.