Design of Liquid Viscosity Measurement System Using Brownian Motion

As the development of science and technology is increasing rapidly, there is one research method that plays an important role in micro-scale measurements, namely Brownian motion. Brownian motion is a phenomenon of the random movement of several particles that can be observed under the objective lens of a microscope due to collisions between particles and surrounding liquid molecules. In this study, the author will observe how the Brownian motion method can be used to determine the liquid viscosity value through the relation between the displacement of polymer particles in various concentration of the solutions and the size of polymer particles that will be used in the observation. The Brownian motion-based system was made with the aim of creating a method of measuring the viscosity of a liquid with equipment that is easier and simpler by utilizing the minimum liquid quantity (in microliters) rather than the conventional methods such as using a viscometer where the quantity of liquid used is large (in milliliters). Measurements were made using the design of optical systems such as camera (Zeiss Axiocam 105 Color) and microscope objective lens (50x magnification). Through the optical system, the movement of particles is then recorded, and the recording image results are processed using image processing algorithms in MATLAB. By using the correlation function, the trajectory of particle movement can be traced until particle displacement data are obtained for each frame (in second). From the experiments that have been conducted using 10-40% glycerin concentrations and 1-micron particle, it shows that the measured glycerin viscosities have good accuracies with the errors no more than 10%. For the measured NaCl viscosities with the concentration variations of 0%, 50%, and 100% using 1-micron particle, it also shows that it has good accuracy with the errors no more than 7%.