Impact-Induced Removal of a Deposited Droplet: Implications for Self-Cleaning Properties

The ability to remove a deposited drop on a substrate is crucial for self-cleaning materials. Here, an approach to achieve the removal of a deposited droplet by employing the impact of a smaller droplet as remover is reported. The results give visible evidence that with the increase of the impact velocity and the size of the impacting droplet, a deposition-to-rebound transition of droplets could occur. Correspondingly, a map showing the relationship between the states of the impacted droplet and the impacting conditions is depicted. More importantly, the proposed model suggests that this novel deposition-to-rebound transition induced by the impact is ascribed to the production of positive excess energy during the process from maximum spreading to complete retraction, which provides the critical value of spreading factor (β) and equilibrium contact angle (θ) for determining whether the transition occurs. Copyright © 2020 American Chemical Society.