Direct observation of dynamic sickling is enabled using a microfluidic chip and the hypoxic environment induced by the protocatechuic acid (PCA), followed by protocatechuate 3,4-dioxygenase (PCD) enzyme. Figure shows the microfluidic observation of in-vitro sickling for SS-RBC from a non-transfused SCD subject with and without sample incubation with a Hb-modifying compound. This technology allows for induction of hypoxia with the maximum deoxygenation rate of about 700-800 tor/min rate correlating to full sample deoxygenation in about 1 min. Progressive sickling of RBC was assessed by time-lapse.