Picture of the Day

Dancing Droplets

Imagine a pin cushion or a lotus leaf where you have an array of fine posts or hairs. Shrink these by about a thousand times and make only the tops and the sides of the posts hydrophilic (liking water), and everywhere else hydrophobic (water-resistant). Now, start putting water on this array of posts. Here you are looking at an optical micrograph where there are tiny droplets of water on top of such posts, but on some, the droplets are so large that they merge with droplets on adjacent posts. It gives the impression that water can dance across the surface. How the topography of the surfaces effects the behavior is critical in the production of many fabrics to make them water repellant.

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©VISUAL, Materials Research Science and Engineering Center, University of Massachusetts, Amherst