Optical spinning rheometry test on viscosity curves of less viscous fluids at low shear rate range

We propose a method, named optical spinning rheometry (OSR), to acquire kinematic viscosity curves of Newtonian and non-Newtonian fluids in the same framework. The OSR is independent of torque measurements and utilizes velocity information measured by particle tracking velocimetry. This optical approach enables flexibility in velocity resolution, and benefits exploring the low shear rate region. In addition, the kinematic viscosity of less viscous fluids like water or dilute polymer solutions can be assessed as being free from the mechanical limitations of torque sensors. The applicable range of the OSR is discussed in detail, and its performance is verified in Newtonian fluids. Demonstrations in dilute xanthan gum solutions, concentrations of O(10ppm)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$O(10~\textrm{ppm})$$\end{document}, show the capability of measuring their shear-thinning behaviors and the kinematic viscosity curves even in the first Newtonian regime.