Development of high-speed sensing technique for blood viscosity with micro-liter sample volume

In the medical field, blood viscosity is known to be correlated with several diseases such as cardiac infarction and brain infarction. The blood viscosity may contribute to detection of diseases at an early stage and may give an indication of health state. There are several methods for measuring blood viscosity such as rotational viscometers and falling ball viscometers, but they need several milliliter sample volume and take several tens of seconds or several minutes to measure. So, we have developed a new viscometer which can measure viscosity within 1 ms and with micro-liter sample volume. In the present study, we have developed a new viscometer by the laser-induced capillary wave using YAG laser. In this paper, first, we have measured viscosities of Newtonian liquids with 90 μl sample volume and showed good agreement within ± 10% from the reference values in the range from 10^-1 to 10 ¹ mPa·s. Then, we have measured healthy human blood with 90 μl sample volume and compared to the reference values. The measured results of blood viscosity and surface tension were 4.5 mPamiddot; and 54 mN/m, respectively. The results were in good agreement with the reference with the estimated shear rate by the present method in the range of 10² to 10³ s^-1.