High-speed sensing of microliter-order whole-blood viscosity using laser-induced capillary wave

Abstract

The present paper introduces an innovative contact-free optical viscosity measurement technique, laser-induced capillary wave (LiCW) using pulsed YAG laser as a heating source, to measure whole-blood viscosity with only a microliter-order sample volume and measurement time on the millisecond order. In this method, interfering pulsed laser beams heat a whole-blood sample and generate a capillary wave, the amplitude of which is less than 10 nm with wavelength of 80-100 lm in the present experiment, caused by a spatially sinusoidal temperature distribution. The damped oscillation of the capillary wave, which is detected by a diffracted probing laser beam at the heated area, provides information regarding the viscosity and surface tension of the whole blood. To demonstrate the validity of the present laser-induced capillary wave viscometer, the viscosity of human whole blood taken from two healthy donors having different hematocrit values was measured using 90 ll sample volumes at 37°C. To consider the feasibility of the present technique for blood rheological studies, we discuss the characteristics of LiCW regarding the non-Newtonian behavior of blood, the velocity boundary layer, the existence of a free surface, and the temperature increase of the blood, and also demonstrate the capability of the method to sense the temporal evolution of blood viscosity with sampling frequency of 0.25 Hz.Keywords Blood viscosity Á Laser-induced capillary wave Á Microliter-order sample volume Á High-speed measurement Á Surface tension Á Thermophysical property sensing

Changes in velocity profile according to blood viscosity in a microchannel

“…In order to overcome these technical limitations of conventional viscometers, several microfluidic devices have been proposed. [10][11][12][13] Nevertheless, these microfluidic platforms also require calibration procedures using a standard fluid as a reference. Moreover, additional procedures with intricate mathematical models are required to measure the viscosity of non-Newtonian fluids.…”

Blood viscoelasticity measurement using steady and transient flow controls of blood in a microfluidic analogue of Wheastone-bridge channel

“…Fluid viscosity was identified using several methods, including micro-cantilever, 12 capacity sensor, 13 capillary force, 14 comparator, 15,16 and laser-induced capillary wave. 17 Most of these methods require fully integrated sensors or additional tedious calibration procedure using a standard reference. On the other hand, viscoelasticity measurement of fluids has been conducted using ferromagnetic micro-beads, 18 optically-induced force, 19 squeeze flows, 20,21 flexible polymer-based deflection, 22,23 micro-PIV, 24 and extensional flow.…”

A review of hemorheology: Measuring techniques and recent advances

“…Conventional methods are the most common and most investigated, but the interest in microsystems for rheological measurements has been growing considerably over the last decade because of the small blood samples required and also because such devices can be cheap, portable and easily disposable, features which are important also for implementation in routine clinical diagnosis. Whatever the technique used, the ideal procedure should: (1) use a small blood sample that can be easily collected from the donor; (2) ensure no blood coagulation during collection and measurement, but avoiding the use of anticoagulant if possible; (3) be able to perform the measurement for a range of relevant temperatures, includ- ing normal body temperature, T 37ºC; (4) enforce simple and straightforward handling of blood sample; (5) provide known and controllable flow kinematics so that the principle of measurement is amenable to analytical mathematical solution (Muramoto and Nagasaka, 2011).…”