The Plant that Cleans Itself

When we’re not cooped up in the house, we like to take a walk around a nearby pond. At this time of year, the pond is quickly filling up with lotus plants (Nelumbo nucifera). Bullfrogs and painted turtles sun themselves on floating pads, while overheated ducklings huddle under raised pads, like resort-goers under beach umbrellas.

Despite growing in an often murky, algae-filled pond and being used as pool floaties by the local wildlife, lotus pads remain stunningly pristine and photogenic. But how can lotus leaves remain clean in such a dirty environment?

The key the lotus pad’s perpetual tidiness is its specialized surface. If you examined a lotus pad up close, and I mean extremely up close, you’d see that the surface is rough, covered in thousands of uneven columns called papillae. These columns are coated in nano-sized hairs, and the entire surface is made of super-resilient wax crystals. When a water droplet hits the surface of a lotus pad, the droplet only makes minimal contact with the tops of all those hairy columns. The water is immediately repelled and forms a sphere. If the pad is disturbed, the water spheres roll over the pad’s surface like so many roombas and pick up any other dirt or debris. Inevitably, the droplets roll off the pad taking any collected grime with them.

Essentially, lotus pads are self cleaning; a phenomenon that is known as the “lotus effect.” This surprising adaptation has inspired engineers to create similar self-cleaning, water-resistant surfaces. In fact, in the near future all of our smartphone screens may be designed to have this very property, and it’s all thanks to Nelumbo nucifera.

Brian Rutter, PhD, is the cofounder of Thing in a Pot Productions and a postdoctoral researcher in plant biology at Indiana University. Subscribe to our newsletter to receive our “Things About Things – Odd Facts About Plants” and video production tips in your inbox every month!

Works Cited:
Ensikat, Hans J et al. “Superhydrophobicity in perfection: the outstanding properties of the lotus leaf.” Beilstein journal of nanotechnology vol. 2 (2011): 152-61. doi:10.3762/bjnano.2.19

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