Study on the shear stress and interfacial friction of droplets moving on a superhydrophobic surface

The variation of velocity field inside a droplet was investigated by particle image velocimetry when the droplet moved on a superhydrophobic surface. Results showed that shear stress increased with the increase of the motion velocity of droplet and droplet viscosity when the motion velocity of droplet increased from 0.3 to 1.1 mm/s and the droplet viscosity increased from 2.69 to 17.41 mPa·s. Moreover, friction force at liquid/solid interface was independent on droplet volume, viscosity and motion velocity on the superhydrophobic surface. It is indicated that the variation of velocity field and shear stress inside droplet was closely associated with the change of the influence depth and the center of mass inside the droplet caused by the substrate. The findings are helpful to understand the motion behaviors of a droplet on the superhydrophobic surface to reduce the energy dissipation when a droplet transport on the superhydrophobic surfaces.