Have you ever looked at windows when it’s raining? Why we can hardly see through some, water makes vision blurry, cloudy. And why with other panes, rainwater does not seem to stay, adhere, or even, it even seems that by sliding, it has cleaned the tile?
franceinfo: Is this phenomenon of sharpness called the “lotus effect”?
Solenne Le Hen: Like a lotus leaf. In nature, the lotus leaf is super hydrophobic, the water drops do not cling, do not adhere but slide on it, roll like marbles, they do not stick to the surface, and at the same time – c This is where nature is good – these drops of water carry away dirt and bacteria in their path. It is a self-cleaning surface.
How it works ?
The details of this mechanism, researchers understood them only about fifty years ago. In fact, the surface of the sheet is rough, tiny roughnesses, we call it the “fakir effect”, as if lots of little nails were preventing water from falling into the interstices. In addition, above this layer of roughness, scientists have discovered carpets of wax crystals, and you know the principle, on an oilcloth, it slips.
It is the same with the lotus leaf. You will tell me, what need did the lotus have to have this hydrophobic system? First, it prevents the sheet from being too heavy in the event of rain, and then it helps to evacuate parasites, dust, dirt or even drops of water that could interfere with photosynthesis. So, we talk about the lotus effect, but we see the same phenomenon with nasturtium leaves, reed leaves and cabbage leaves.
You told us about windows, what are the other possible applications in our everyday life?
In the same spirit, there is the rainproof windshield for cars, planes or any other means of transport. The lotus effect is also already applied to anti-fog goggles and anti-frost coatings. We can also imagine protecting the electrical cables against the rain. This principle is also found in self-cleaning paints affixed to building facades. The lotus effect also helps to fight against corrosion.
And then some companies launched lotus-textiles. What is practical is that they do not get dirty, you can jump with both feet in the mud, and your shoes stay white. Another example, compared to a classic T-shirt, your lotus-effect T-shirt is less wet, water or perspiration soaks in less, and the fabric breathes more.