- The measurement of extensional viscosity is important in many chemical, biomedical, agricultural, and engineering applications. The determination of extensional viscosity is generally difficult, expensive, and inaccessible outside of research labs. The development of a smartphone application (app) that could use a phone’s high-speed camera to measure this parameter could open doors for easy, cheap, mobile, and accessible measurements. In this study, a MATLAB script was developed to process and analyze videos taken by an Apple iPhone of a fluid being stretched between two surfaces then thinning until separation. The MATLAB script is used to extract information about the elasticity of various fluids. The materials chosen for use in this study were selected to represent materials that are easily accessible to most people. Ideal video-taking conditions were determined then used to take several videos of Newtonian and non-Newtonian fluids. When the extracted extensional relaxation time was compared to a recently developed technique called “optically-detected elastocapillary self-thinning dripping-onto-substrate” (ODES-DOS) the values were consistently higher by about 3 ms. However, both methods had similar extensional relaxation time vs PEO concentration trends with slopes of 0.67 for the ODES-DOS method and 0.62 for the smartphone video method. This shows that an iPhone app could be used in the field for rough measurements of the extensional viscosity of fluids which could also be used for precise qualitative comparisons given measurements of multiple samples. Neither the height the fluid was stretched, nor the amount of fluid stretched was found to significantly affect the values obtained.
Key Words: Extensional Viscosity, Smartphone Application, Rheology, Non-Newtonian Fluid Dynamics, Polymers