Development of pulsed laser viscometer (Development of automatic high-speed measuring apparatus for viscosity by near-infrared laser-induced capillary wave method)

Abstract

We have developed a pulsed laser viscometer (PLV) which is a high speed viscosity sensing technique using pulsed volume heating laser of near-infrared wavelength. For the purpose of developing the novel viscometer applicable to the in-situ measurement and the high time-resolution sensing of viscosity change process, the liquid-level height is a critical factor because the principle of this method is based on the physical phenomenon near the surface. Therefore, we developed the liquid-level control system for precisely adjusting the height. This system determines the liquid-level by controlling the sample stage to the target height with the reflected beam of a probing laser. In addition, we fully automated the measurement process for high speed sensing. The automatic system enables to measure viscosity in a few seconds after setting the sample. In this paper, with the developed experimental apparatus, in order to confirm the capability of the liquid-level control system, we successively measured viscosities of four different Newtonian liquids (toluene, water, 1-hexanol and JS20), whose viscosity range is from 0.1 to 10mPa･s. Then each measurement time was within 3~4 seconds and the deviations from the reference values were within ±10.7 %. In addition, as the aim for a verification of viscosity sensing, we measured viscosity of toluene with intervals of 1 second for 20 seconds. Finally, we successively measured the whole human blood viscosity at the coagulation process.