The detachment of droplets from a rotating structure with micro-pillar surface

Inspired by the wriggling motion of mammals after bathing, it has been discovered that centripetal acceleration can effectively remove droplets. Since rotation emerges as a viable method for this purpose, it is essential to understand the interaction between droplets and rotating structured surfaces. In this study, we numerically investigate the dynamic behavior of droplets and the factors influencing droplets' detachment from a rotating brush-like surface with micro-pillars by employing many-body dissipative particle dynamics. We identify three distinct droplet motion modes: remaining on the surface (Scenario I), undergoing pinch-off (Scenario II), and direct detachment within two rotational cycling periods (Scenario III). Furthermore, regardless of the mode, the center-of-mass velocity of the droplet along the z-axis changes synchronously with the angular velocity direction of the brush-like structure. Our results demonstrate that increasing the rotation radius and reducing the rotation period act synergistically to promote droplet detachment. Additionally, two distinct modes of direct detachment are observed. A critical Weber number (We) is identified for the transition from the stretching mode to the peeling mode, governed by the balance between adhesion force and centripetal force. This study offers valuable insights into active water removal and droplet manipulation techniques.