Application of laser-induced capillary wave for a new viscosity measurement method (theory and experimental apparatus for measuring wide range of viscosity)

The viscosity is one of the very important thermophysical properties for food industry and it is required to develop a new technique which is possible to measure significantly changing viscosity by single apparatus. In the present study, we have developed a new viscometry based on a laser-induced capillary wave technique by using a pulsed CO₂ laser as a heating source. The detected signals for several Newtonian liquids such as acetone, toluene, water, ethanol, 1-hexanol, decanol, ethylene glycol, glycerol, JS 100, JS 1000 and JS 14000 having wide range of the viscosity (10^-1-10⁴ mPa·s) agreed well with the theoretical calculations. It is also confirmed that in the viscosity range 10¹-10³ mPa-s, the viscosity can be determined by calculating decay time constant of detected signals. We have demonstrated that the application of the laser-induced capillary wave technique has considerable potential for the measurement from low to high viscosity liquids.