Dynamical behaviors of droplet impingement and spreading on chemically heterogeneous surfaces

By using many-body dissipative particle dynamics (MDPD), dynamical behaviors of droplet impingement and spreading on chemically heterogeneous surfaces is presented in this paper. The influences of Weber number (We) and fraction (Φlicratio of hydrophilic area to whole region) on dimensionless spreading diameter (D* ratio of spreading diameter to initial droplet diameter), dimensionless height (H* ratio of height of droplets to initial droplet diameter), advancing contact angle (θa) and receding contact angle (θr) are systematically analyzed. The simulated results show that larger We and Φlic lead to larger spreading diameter, even overspreading. Particularly, the stick-slip motion of droplet during recoiling stage is found to be affected both by Weber number (We) and fraction (Φlic), which cannot be captured on homogenous surface. As a result, the stick-slip motion could be divided into two sub-stages during recoiling stage, which is novel to the situation involving droplet with fixed impact velocity. It provides an insight to understand the mechanism of stick-slip motion for droplet impingement on chemically heterogeneous surfaces.