Novel optical viscosity sensor based on laser-induced capillary wave

In recent years, viscosity has been one of the most important thermophysical properties, and its new sensing applications in a noninvasive method with small sample volume are required in a broad field. For example, in the medical field, the viscosity of body fluid, such as blood, is an essential parameter for diagnosis. In the present study, we have developed a new miniaturized optical viscometer, namely MOVS (Micro Optical Viscosity Sensor), which is applicable to the noninvasive, high speed, small sample volume, in situ and in vivo measurement of a liquid sample in both medical and industrial fields based on laser-induced capillary wave (LiCW) technique. In our experimental setup, two excitation laser beams interfere on a liquid surface and generate the LiCW. By observing the behavior of the LiCW using a probing laser, which contains the surface information of the sample liquid, viscosity and surface tension can be obtained. In this paper, the fabrication of prototype MOVS chip using micro-electro mechanical systems (MEMS) technology for the first time and the discussion of the validity of the viscosity measurement are reported. Preliminary measurement using distilled water was demonstrated, and nanosecond order high speed damping oscillation was successfully observed.