Engineering Nature: Lotus Leaf
Continuing with the current blog series that examines biomimicry in engineering, this week’s blog will examine the interesting properties of a lotus leaf, or the so called “Lotus Effect”, and how they can be applied to current engineering advances in housewares, spacesuits, and even power plants. In some Eastern cultures the lotus plant is a symbol of purity due to its unprecedented hydrophobic and self-cleaning properties. By examining and attempting to harness these properties, current mechanical engineers are working to create a more efficient and cleaner version of current products.
Engineering Mechanics Behind It
The first line of defense between the lotus leaf and water is tiny wax-like crystals that coat the surface of the leaf. Because these crystals are so small, measuring only one nanometer across in most cases, they do not stop the water from sliding down the leaf, however, they are large enough to create a rough surface where water has difficulty adhering.i This difficulty comes from what is known as the contact angle. In most plants, or leaves, that display extreme hydrophobia, such as the lotus, contact angles can be as high as 162o, thus drastically lowering the contact area between the water and the leaf.ii The bumps created by the tiny crystals also serve another purpose in terms of the self-cleaning process of the leaves. On a perfectly smooth surface, a water droplet will slide down and pick up as much dirt as its contact area with the surface can hold. In the case of the lotus however, these bumps force the water to roll and tumble which causes the entire surface of the droplet to pick up dirt. The plant’s second line of defense is designed to repel the condensation that forms and cannot simply roll off the leaf. Because the lotus leaves are long and have fairly slender stems they are shaken by even a slight breeze or subtle vibration. When these subtle vibrations disturb the leaves, tiny hairs, which grow from each waxy bump, essentially drag the sticky condensation out of the small nooks and crannies on the leaf surface. iii
Applications and Innovations
Currently the Lotus Effect is being researched in almost every field imaginable, from outer space to coffee cups and everywhere in between. Right now the most commonly desired use that electrical engineers are looking into is hydrophobicity in electronics and power plant items. Many high performing electronics must be cooled by removing heat through water evaporation which in turn causes condensation. Using lotus leaf technology to then remove this condensation would not only increase the rate at which you could cool the electronics but increases electronics reliability and removes the fear of water contaminating the electronics. Engineering researchers at Duke’s Pratt School of Engineering have also been testing the lotus effect in harsh humid and cold environments where condensation naturally occurs. Utilizing the Lotus Effect would allow an entirely improved design of textiles and optics that do not become wet or fog in environments such as Antarctica. On a smaller scale, a new company based out of New Mexico, Lotus Leaf Coatings Inc.(TM), has patented a spray coating that has Lotus Leaf like properties and this technology can be applied to a large variety of fields such as sanitation, HVAC, as well as many consumer products. They even have begun working with car and plane designers to implement the technology in order to create a vehicle that never requires washing, thus saving immeasurable amounts of water and energy.
The Louts Effect is just one aspect of taking nature and applying it to the many disciplines of science and engineering. By mimicking nature and it’s advances scientists can create products that are not only environmentally friendly and economical, but continue to push the boundaries of technological advances already being made.
iInglis-Arkell, Esther i09 “Superhydrophobia Spawns the Lotus Effect” Jan 1, 2013
iiEnsikat, Hans. Ditsche-Kuru, Petra. Neinhuis, Christoph. Barthlott, Wilhelm. US National Library of Medicine and
National Institute of Health “Superhydrophobicity in Perfection: The Outstanding Properties of the Lotus Leaf” March 10,
iii Salton, Jeff Gizmag “Good Vibration: Lotus Leaf Secrets Revealed” October 25, 2009