Effect of surface roughness on the angular acceleration for a droplet on a super-hydrophobic surface

The motion of droplets on a super‐hydrophobic surface,whether by sliding or rolling,is a hot research topic.It affects the performance of super‐hydrophobic materials in many industrial applications.In this study,a super‐hydrophobic surface with a varied roughness is prepared by chemical‐etching.The adhesive force of the advancing and receding contact angles for a droplet on a super‐hydrophobic surface is characterized.The adhesive force increases with a decreased contact angle,and the minimum value is 0.0169 mN when the contact angle is 151.47°.At the same time,the motion of a droplet on the superhydrophobic surface is investigated by using a high‐speed camera and fluid software.The results show that the droplet rolls instead of sliding and the angular acceleration increases with an increased contact angle.The maximum value of the angular acceleration is 1,203.19 rad/s^(2) and this occurs when the contact angle is 151.47°.The relationship between the etching time,roughness,angular acceleration,and the adhesion force of the forward and backward contact angle are discussed.