title: How does an air film evolve into a bubble during drop impact?
abstract: When a liquid drop impacts a solid surface, air is generally entrapped underneath. Using ultrafast x-ray phase-contrast imaging, we directly visualized the profile of an entrapped air film and its evolution into a bubble during drop impact. We identified a complicated evolution process that consists of three stages: inertial retraction of the air film, contraction of the top air surface into a bubble, and pinch-off of a daughter droplet inside the bubble. Energy transfer during retraction drives the contraction and pinch-off of a daughter droplet. The wettability of the solid surface affects the detachment of the bubble, suggesting a method for bubble elimination in many drop-impact applications.
authors.affiliation: X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, Korea.
authors.forename: Ji San
authors.initials: JS
authors.lastname: Lee
authors.forename: Byung Mook
authors.initials: BM
authors.lastname: Weon
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Je
authors.forename: Kamel
authors.initials: K
authors.lastname: Fezzaa