© 2019 by Dan Daniel

Lotus-effect surfaces

One who performs his duty without attachment, surrender the results unto the Supreme God, is not affected by sinful actions,

as the lotus leaf is untouched by water

 

                                                                  Bhagavad Gita

For centuries, the lotus has been held as a symbol of purity by various Eastern traditions—the lotus grows on muddy water, yet its leaves remain unsullied and untouched by water. Yet, it was only in the 1990s that the origin of this water-repellency or lotus-effect superhydrophobicity was understood. The leaf of a lotus and of many other plants are covered by micro- and nano-roughness, such that a water droplet can bead up into a ball that sits on top of the petrusions, like a “fakir on a bed of nails” (L. Mahadevan). The resulting fakir droplet has a high contact angle θ > 150◦ and can roll away at the slightest tilt < 5◦.

20 μm

Micro-/-nanostructures

source: wikimedia

Droplets bounce off such surfaces with remarkable ease, as demonstrated by high-speed videos shown below.

I am interested in explaining the origin of this extreme liquid-repellency by experimentally visualizing the details of the droplet-solid contact and correlating it with the pinning force acting on a droplet.

 

The details of this work can be found here.