Effect of Wettability on Micro- and Nanostructure Surface Using Sessile Droplet Contact Angle for Heat Transfer Application

This experimental investigation studied the variation in the dynamic contact angle measured on copper surface roughened by emery with grit size of 320, 600, 1000, 1500 and 2000 and titanium oxide nanoparticle-coated nanostructure with thickness of 250, 500, 750 and 1000 nm on copper substrates by e-beam evaporation process using deionized water as liquid with the help of macroscopic contact angle meter. In case of emery-roughened copper, advancing contact angle increases with the increase in emery grit size. For nanoparticle-coated surface, initially with the increase in coating thickness from 250 up to 750 nm, advancing contact angle increases; after that, further increasing in coating thickness to 1000 nm, advancing contact angle diminishes. Generally, the contact angle was found to vary from 30 degrees to 60 degrees for deionized water droplet for the nanoparticle-coated surface having different thickness. The surfaces are characterized with respect to morphology and topography to know the particle size and shape and particle distribution pattern and surface roughness with the help of AFM and FEG-SEM. The theoretical analysis is also carried out to determine the dependency of contact angle and roughness on the nanoparticle-coated titanium oxide thin-film surface. This formulation qualitatively showed a similar trend with experimental results.