Surface wettability through asymtotic contact angle

The purpose of this investigation is to find a unique and accurate criterion to measure surface wettability. The asymptotic contact angle (droplet contact angle in no gravity condition), which is independent of droplet size, is used to identify the surface wettability in this work. The asymptotic contact angle is calculated by equating the normal component of interfacial force on an axisymmetric droplet and spherical droplet. The effect of 2.5 nm bismuth telluride nanoparticles on surface wettability is measured and evaluated by asymptotic contact angles as a sample. This paper also studies the effects of nanoparticles on solid, gas and liquid interactions at the triple line as well as the gas-liquid surface tension of aqueous solutions of 2.5 nm bismuth telluride nanoparticles functionalized with thioglycolic acid. Experimental measurements of nanofluid droplet shapes show that the contact angle strongly depends on nanoparticle concentrations. Fitting the droplet shape with predictions of the Laplace-Young equation, the nanofluid gas-liquid surface tension is determined.