Self-Cleaning Materials: A Nano-Technology Wonder

Have you ever wondered how these paints, glass windows, and fabric companies claim that their material is self-cleaning and lasts for years? Maybe yes or maybe no. Such upgrades in these everyday use items are due to the “Self-Cleaning Technology” a wonder of Nano-Technology (Manipulation of atoms and molecules at a nanoscale). Nanotechnology has been a hot topic for researchers in materials engineering, electrical engineering, physics, and much more on for a couple of decades now. This technology is doing wonders and maybe is going to change this world in the coming time. In addition, the speed with which this technology is growing and giving breakthroughs every day maybe our generation or the next generation will be able to witness the “Future”.

Lotus Leaf: The incredible property of Lotus leaf (on the left) is self-cleaning is the basis of self-cleaning. The microstructure (on the right) represents the grooves on the leaf which is the reason behind this property.

Self-Cleaning Technology is one of the wonders of nanotechnology. The first Self-Cleaning surface was created in 1995 artificially by Paz et al (Paz Y, 1995). The concept of this technology was taken from the natural self-cleaning phenomenon of Lotus Leaf in which water rolls across a leaf without sticking and carries away the dirt leaving a dry and clean leaf behind. Microscopic bumps all over the surface of the leaf are the reason for its hydrophobic properties, which is why it was called "Lotus Leaf-Inspired Nanotechnology" by Scientific American in August 2008 (American, 2008). Moreover, some other natural phenomenon like shark’s skin, gecko feet, butterfly wings, etc. were inspirations behind the development of this technology.

The heroes of this technology are TiO2 and ZnO. TiO2 nanoparticles are coated on the surface and ZnO is used as a catalyst during self-cleaning. Just like wax, which allows water to slip on it, TiO2 coating makes water to slip and clean the material. SnO2 instead of TiO2 can also be coated to make the coating hydrophilic.  After the selection of coating, the most important thing is the wetting angle or wettability or stickiness of the cleaning surface. This wetting angle can be calculated using different models like Young’s model, Wenzel’s model, etc. but Young’s model is mostly used. Now both hydrophobic and hydrophilic coatings are used. For hydrophobic coatings wetting angle is high as 180 degrees and for the hydrophilic wetting angle is low as 2-3 degrees maximum. Other properties like photocatalysis and optical properties are considered as well.

Self-Cleaning Application: Self-cleaning glass has extraordinary optical properties. the Titanium Oxide coating breaks down the organic matter, blocks harmful radiations and glare.

Most of the applications of this technology are in the paints industry, water filtration, glass windows, etc. One of the Multinational company AkzoNobel has created a paint that lasts for 16 years. It is a huge claim even their manager Jenny Lundegård on October 2014 reportedly said:

It is a huge claim, but we’re standing by it and are very confident in what we’re saying (Knowles, 2014)

Moreover, we are aware of filtered water and most of us use it every day. Right now, multinationals companies like NESTLE and THAMES887 WATER(UK) use filtration plants in which the filters used are coated with self-cleaning particles. In this way water as well as the filter is kept clean. This technique is used not only in water industry but in the food industry as well like M&M’S, MARS, COCA-COLA, etc. self-cleaning glass is invented which in near future is going to be used in cars as well as house windows, a Multinational car company NISSAN has used this technology in one of its cars. Even self-cleaning fabric is invented as well.

The wonders of Nanotechnology are being applied everywhere and the beautiful part of this is it is being used in almost every part of everyday life from drinking water to wearable clothes from food to wall paints. There is no doubt that nanotechnology is the future. But the future which we imagine today, will this become a reality? Let’s see……..

References:

American, S. (2008, Aug). Self-Cleaning Materials: Lotus Leaf-Inspired Nanotechnology. Self-Cleaning Materials: Lotus Leaf-Inspired Nanotechnology. Retrieved from https://www.scientificamerican.com/article/self-cleaning-materials-inspiration/

Knowles, W. (2014). 2degreesnetwork. Retrieved from 2degrees: https://www.2degreesnetwork.com/groups/2degrees-community/resources/how-this-paint-can-clean-itself-and-last-16-years/

Paz Y, L. Z. (1995). "Photooxidative self-cleaning transparent titanium dioxide films on glass". "Photooxidative self-cleaning transparent titanium dioxide films on glass". Retrieved from https://www.cambridge.org/core/journals/journal-of-materials-research/article/photooxidative-selfcleaning-transparent-titanium-dioxide-films-on-glass/89906DC226A576B38CC4178CCDE7A35F

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