Mechanical impact on a breath figure

We present here the effect of mechanical vibrations on a breath figure. By impacting a falling steel ball on a plastic plate covered on its bottom side by a breath figure, we show that in a few milliseconds, the figure can evolve even more dramatically than it would in minutes in the natural aging process. We quantify the variations of droplet number and sizes with time for various substrate accelerations and mean initial droplets radii. We show that, above an acceleration threshold, the final number of droplets decreases more and more with acceleration. We interpret this result by the contact line unpinning provoking oscillations of the droplets radii, which makes the drops contact and coalesce with neighbors. Finally, we introduce a new parameter to characterize the droplet number decrease. We have plotted it as a function of an effective Bond number built with the substrate acceleration and mean droplet radius. Interestingly, all the data fall on a single master curve.

Automated summary

We demonstrate the impact of mechanical vibrations on a breath figure by dropping a steel ball on a plastic plate covered with a breath figure pattern. The evolution of the figure can occur in milliseconds, showing a more dramatic change than the natural aging process that takes minutes. We quantify the changes in droplet number and size over time for different substrate accelerations and initial droplet radii. It is observed that above a threshold acceleration, the final droplet count decreases as acceleration increases. This can be explained by the unpinning of the contact line causing oscillation of droplet radii, leading to contact and coalescence with neighboring droplets. Additionally, a new parameter is introduced to characterize the decrease in droplet number, which shows that all the data follows a single master curve when plotted against an effective Bond number.