Combining Nanotechnology with Nature to Create Waterproof Coatings for Leather and Textiles

Image Credits: shutterstock.com/Volodymyr Plysiuk

The production and consumption of consumer goods is constantly increasing in today’s society. Goods are made and sold cheaply, break, or become obsolete quickly and are substituted in a cycle that produces huge quantities of waste.

The consumer cycle reduces the world’s natural resources and results in the production of huge quantities of waste to be disposed of frequently, at high cost to the environment.

Textile goods, such as shoes and clothes, are mostly problematic for the environment. Shoes and clothes can be manufactured and sold very cheaply; they are washed regularly and then unavoidably thrown away when they start to appear old.

Laundering clothes frequently adds to the already existing environmental concerns; excessive water and energy usage, pollution by detergents and the discharge of microscopic plastic fibers from synthetic fabrics all present a threat to the environment. One way of fighting the pollution and waste linked with the textile industry is by manufacturing goods that are easy to clean without detergents, durable and maintain their ‘new’ appearance.^1,2,3

In the recent years, there has been an increase in nanotechnology research, and nanotechnology has been incorporated into many applications in everyday life. The Nanotechnologists at Nanex have currently drawn inspiration from nature to create a new coating for textiles and leather that repels dirt and water, allowing the manufacture of shoes and clothes that are water-resistant, self-cleaning and durable. Self-cleaning clothes could positively influence the environment by minimizing energy consumption, water consumption and pollution from detergent and plastics fibers.⁴

Inspiration from Nature: The Lotus Plant

The coating created by Nanex draws its inspiration from the properties of the lotus plant.⁴ Lotus plants grow in muddy, semi-aquatic environments, but have an inherent ability to remain dirt-free as their leaves are water-repellent and have self-cleaning surfaces.

When a water droplet falls on the surface of a lotus leaf, it beads up into a nearly perfect sphere and easily rolls off the leaf. As the water rolls off the leaf, it picks up and carries away any dirt or dust, resulting in a self-cleaning surface.^5,6

To establish how water-repellent a surface is, Researchers study the shape that a water droplet makes on the surface, and the angle formed by the surface of the liquid and the contact surface, referred to as the contact angle.

The larger the contact angle, the lesser the liquid will spread on the surface, and the more water-repellent the surface is. A high contact angle with water (>90°) is linked with a hydrophobic, water-repellent surface. Surfaces with a contact angle with water of more than 150° are called superhydrophobic surfaces. Both the lotus leaf surface and the surfaces covered in Nanex coating are superhydrophobic.^7,8

The lotus leaf’s superhydrophobicity is due to the chemistry and the hierarchical topography of the leaf’s surface. When water falls on the leaf's surface, the rough texture of the surface provided by microscale ‘bumps’ results in trapped air and decreased contact between the surface and the water. Therefore, the attractive forces between the water molecules are more than the attractive forces between the surface and the water molecules, causing a water droplet to form.

Nanoscale hairs on the microscale ‘bumps’ of the lotus leaf further decrease the contact between the surface and the water molecules, causing superhydrophobicity. Nanex coatings make use of nanostructures in a similar way to the lotus leaf, leading to the creation of water-repellent, self-cleaning textile surfaces.^4-6

Image Credits: shutterstock.com/aeiddam0853578919

How Nanex Coatings Work

Nanex coatings work in a similar manner to the lotus leaf. The coating covers every fiber of the original fabric and forms nanostructures on the surface of the fabric. When water falls on the surface, air is trapped by the nanostructures, and as the attractive forces between the water molecules are more than the attractive forces between the surface and the water, a droplet forms that slides off the surface, taking with it any dirt that is present.

Nanex coatings, thus, render the fabric water-repellent and protect against stains, while preserving the look, feel and breathability of the original fabric. Nanex coatings have already found many applications and can be applied using an aerosol to any natural fiber (see video). Jasna Rok and Elegnano have partnered with Nanex to create water and stain resistant shoes and clothing using Nanex coatings.^9,10

Conclusion

In summary, consumerism results in many environmental problems including the depletion of energy, natural resources and water. Shoes and clothes that are washed regularly add to further detrimental effects on the environment due to pollution caused by plastics fibers and detergents.

Nature has inspired some Nanotechnologists to develop coatings that render leather and textiles water-resistant and self-cleaning, decreasing their environmental impact. Research at Nanex is currently focused on creating anti-odor sprays that eliminate odor particles, further minimizing the need to wash clothes.

References

1. Claudio L, Waste Couture: Environmental Impact of the Clothing Industry. Environmental Health Perspectives 2007 115(9):A449-A454.
2. Hartline NL, Bruce NJ, Karba SN, Ruff EO, Sonar SU, Holden PA, Microfiber Masses Recovered from Conventional Machine Washing of New or Aged Garments. Environmental Science & Technology 2016 50(21):11532-11538.
3. Saouter E, van Hoof G, A Database for the Life-Cycle Assessment of Procter & Gamble Laundry Detergents. The International Journal of Life Cycle Assessment 2002 7(2):103-114.
4. https://nanexcompany.com/ Accessed June 12^th, 2017.
5. Ensikat HJ, Ditsche-Kuru P, Neinhuis C, Barthlott W, Superhydrophobicity in perfection: the outstanding properties of the lotus leaf. Beilstein Journal of Nanotechnology 2011 2:152-161.
6. Latthe SS, Terashima C, Nakata K, Fujishima A, Superhydrophobic surfaces developed by mimicking hierarchical surface morphology of lotus leaf. Molecules 2014 19(4):4256-4283.
7. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Liquids/Contact_Angles Accessed June 12^th, 2017.
8. http://iopscience.iop.org/article/10.1088/0034-4885/78/8/086501/meta# Accessed June 12^th, 2017.
9. http://www.elegnano.com/ Accessed June 12^th, 2017.
10. http://www.jasnarok.com/ Accessed June 12^th, 2017.

This information has been sourced, reviewed and adapted from materials provided by Nanex.

For more information on this source, please visit Nanex.