Sessile droplet contact angle of water-Al2O3, water-TiO2 and water-Cu nanofluids

This work presents measurements of the contact angle of sessile droplets for three nanofluids, i.e. water-Al2O3, water-TiO2 and water-Cu. The plates made of glass, anodized aluminium and stainless steel of different roughness served as substrates. Ultrasonic vibration was used for 30-60 min in order to stabilise the dispersion of the nanoparticles. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. Three methods of contact angle measurement were applied. The contact angle was established directly by use of a KRÜSS DSA10 goniometer or - building on digital images of droplets, an appropriate geometrical approach and tangent methods were applied. The study revealed that the droplet contact angle of nanofluids depends on surface roughness, type of substrate, material of nanoparticles, and concentration of nanoparticles.