Evaluation of three methods of static contact angle measurements for TiO2 nanofluid droplets during evaporation

Abstract

This article discusses the evaluation of three methods of static contact angle measurements of de-ionized (DI) water and TiO2 nanofluid droplets with three concentrations (0.5%, 1%, and 5%) that evaporate on the substrate of three different temperatures. To compare the discussed approximation methods, the differences between the results of the mean contact angles were identified; the highest standard deviation was recorded for the Young–Laplace and circle methods, such as for the nanofluid TiO2–DI with 1% at 50 °C, it is 3.21°, while the lowest value was obtained for TiO2–DI with 5% at Tenv, SD = 0.04°, by comparing the contact angle results using the ellipse and circle methods. Research shows that circular shape approximation is not to be excluded for contact angle determination in the angular range of 0°–75°.