Bubble shapes and their changes on slippery surfaces during directional transportation.

Bubble manipulation in aqueous environment has attracted much attention due to its large-scale applications. Meanwhile, the bubble shapes on solid surface had played an important role in bubble manipulation. In this work, four types of bubble shape have been summarized of bubble on the slippery surface affected by the bubble volume, stripe width and substrate wettability. Understanding bubble shapes on narrow slippery stripes and how they change during manipulated processes is significant for both industrial and daily life applications. Moreover, bubble shapes are mainly affected by bubble volume, stripe width and substrate wettability. Revealing the relationship between those factors for bubble shapes is crucial for further study. While there are many studies of bubble manipulation underwater on slippery surfaces, the detailed evolution of bubble shapes on those substrates is still worthy of further study. In this research, the details of bubbles shapes in different conditions were studied and analyzed. Air bubbles were continuously released on substrates with different chemistries and different geometric parameters to study their effect on bubble shape evolution. Bubble shape can be categorized into four states according to the relationship between bubbles and the stripe widths. Bubble shapes have considerable differences in their top-view and side-view under each state. Furthermore, during the directional transportation of bubbles on a wedge-shaped slippery surface, bubble shapes change from the tip to the end by the width gradients. The outcomes of this work broaden the horizon for the understanding of bubble shapes on slippery surfaces and their changes during transportation. [ABSTRACT FROM AUTHOR]