Multiple-parameter sensing using an autonomous blood flow in a microfluidic chip

Measuring many blood parameters simultaneously enhances the detection of minor abnormalities and sharpens the diagnostic specificity compared with single-parameter tests. The previous methods require precise blood-flow rate control using bulky syringe pumps. To resolve this, we propose a novel method for quantifying multiple parameters of blood rheological properties using a microfluidic chip. A portable compliance pump consisting of an air compliance unit and three-way stopcock is used to load the test blood onto a microfluidic chip, which is composed of an inlet port, main channel, and outlet reservoir. Under continuous blood flow in the main channel, three test channels are bifurcated from the main channel. To set blood flow autonomously (i.e., forward, reverse, and stop), the end of each test channel is connected to air damper. By analysing the time-lapse image intensity of the blood flow in the test channel (Itc), the onset time of the flow reversal (trf) is calculated and suggested as the equivalent fluid viscosity. Representative aggregation parameters (tAI, AIsm, and AIPM) are obtained to quantify red blood cell (RBC) aggregation. Representative parameters of sedimentation (tESR, ESRsm, and ESRpm) are acquired by analysing the time-dependent image intensity of the blood flow in the main channel (Imc). According to the experimental validations, the onset time of the flow reversal is linearly proportional to the fluid viscosity. Through experimental analysis of time-dependent Itc and Imc, all suggested parameters consistently reflect changes in haematocrit, blood medium, and RBC stiffness. The proposed method can be considered a potential method for probing multiple blood parameters (viscosity, aggregation, and sedimentation).