The individual effects of plasma and red blood cells (RBCs) on the biophysical properties of blood can be monitored by measuring erythrocyte sedimentation rate (ESR) and RBC deformability simultaneously. However, the previous methods require bulky and expensive facilities (i.e., microscope, high-speed camera, and syringe pump) to deliver blood or capture blood flows.
To resolve these issues, a simple method for sequential measurement of ESR and RBCs deformability is demonstrated by quantifying cell-free volume (VCF), cell-rich volume (VCR), and blood volume (VB) existed inside air-compressed syringe (ACS). A microfluidic device consists of multiple micropillar channels, an inlet, and outlet. After ACS is filled with air (Vair = 0.4 mL) and blood sample (VB = 0.6 mL, hematocrit = 30%) sequentially, the ACS is fitted into inlet. The cavity inside ACS is compressed to Vcomp = 0.4 mL after closing outlet with a stopper. A smartphone camera is employed to capture variations in VCF, VCR, and VB inside ACS. ESR index suggested in this study (ESRPM) is obtained by dividing VCF (t = t1) with an elapse of t1. By removing stopper, ΔVB (ΔVB = VB [t = t1] – VB) is obtained and fitted as a two-term exponential model (〖∆V〗_B=a exp [b t]-c exp[-d t]). As a performance demonstration, the proposed method is employed to detect ESR-enhanced blood sample, homogeneous hardened blood sample, and heterogeneous blood sample.
From the experimental results, it is found that the proposed method has the ability to detect various bloods by quantifying ESRPM and two coefficients (a, b) simultaneously.
In conclusion, the present method can be effectively used to measure the ESR and RBCs deformability in resource-limited settings.

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