The Effect of a Magnetic Field on the Profile of Sessile Magnetic Nanofluid Droplets

Abstract

Surface wettability plays an important role in droplet formation, removal, and resistance to fouling. The sessile droplet profile is one of the most important parameters characterizing surface wettability. In this study, an investigation was carried out into the effects of a magnetic field on the profile of sessile droplets of magnetic nanofluid. We started with a revision of the classic Young–Laplace equation according to normal stress balance principles by considering a magnetic nanofluid droplet in an applied magnetic field gradient. The secant method was then used to solve the non-linear differential equation and predict the sessile droplet profile. The results showed that a downward magnetic force caused an expansion of the profile and an upwards magnetic force caused contraction. In other words, droplets on an hydrophilic or hydrophobic surface could be tuned by magnetic field gradients of different strength and direction. This magnetowetting effect could be further adjusted by selection of different fluid, material, and particle concentration.