Abstract
Hematocrit-insensitive Absolute Blood Flow Rate Measurement in 0.5-mm-diameter Flow Channel Using MEMS-based Laser Doppler Velocimeter with Signal Modification for Detecting Beat Frequency from Broad Power Spectrum
Highlights
Microfluidic device technology is becoming increasingly important in the biomedical field.[1]
Several types of flow sensors for microfluidic devices have been developed, the measurement principle of which is based on thermal transport,(21) electrical admittance change,(22) f luid dynamical oscillation,(23) optical imaging,(24) and the laser Doppler effect.[25]. A laser Doppler velocimeter (LDV) achieves contactless measurement in real time without the need to add anything to the measurement target, because an LDV detects velocity from the Doppler shift of scattered light, which is proportional to the velocity of the measurement target
During the f low measurement of a thicker blood f low layer (i.e., >400 μm for 40% hematocrit), the power spectrum of the LDV signal is greatly broadened and the signal weakened owing to marked light scattering and absorption by red blood cells (RBCs), resulting in a difficulty in detecting beat frequency because of the Doppler shift required for the calculation of f low velocity.[31]. It is known that the blood flow rate can be evaluated by laser Doppler flowmetry (LDF) even with a broad power spectrum
Summary
Microfluidic device technology is becoming increasingly important in the biomedical field.[1]. Several types of flow sensors for microfluidic devices have been developed, the measurement principle of which is based on thermal transport,(21) electrical admittance change,(22) f luid dynamical oscillation,(23) optical imaging,(24) and the laser Doppler effect.[25] A laser Doppler velocimeter (LDV) achieves contactless measurement in real time without the need to add anything to the measurement target, because an LDV detects velocity from the Doppler shift of scattered light, which is proportional to the velocity of the measurement target. During the f low measurement of a thicker blood f low layer (i.e., >400 μm for 40% hematocrit), the power spectrum of the LDV signal is greatly broadened and the signal weakened owing to marked light scattering and absorption by red blood cells (RBCs), resulting in a difficulty in detecting beat frequency because of the Doppler shift required for the calculation of f low velocity.[31] It is known that the blood flow rate can be evaluated by laser Doppler flowmetry (LDF) even with a broad power spectrum. In the LDF method, the measured value varies depending on the hematocrit value,(28) which varies greatly among individuals (i.e., 40 to 54% for men, 36 to 48% for women[32]), preventing an absolute f low measurement of blood
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