Hydrophobic surfaces

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Many years ago I worked as a polymer physicist and I still occasionally read polymer journals. I recently came across an article on superhydrophobic surfaces which use nanoscale structural elements to repel water. Water falling on them forms beads and rolls off. The article put me in mind of Lady’s Mantles, a beautiful group of plants that are grown in gardens as ground cover and are common in the wild in Britain.

Many species of Lady’s Mantle have hydrophobic leaves. The dense arrangement of hairs are such that the stable state for water in contact with the surface is a droplet or bead rather than the usual thin film. After rain, the beads make lovely subjects for macrophotography.

Beads of water on Small Lady's Mantle Alchemilla glaucescens in Scotland
Close view of the water droplets

The droplets were considered to be the purest form of water by alchemists. It’s easy to see why as they sparkle in the sun. Some even gathered the droplets for use in vain attempts to turn base metals into gold. It is from this practice that the Latin name for Lady’s Mantles, Alchemilla, is derived.