A group of researchers located in Australia at Monash University in Victoria are developing a process that could lead to self cleaning wool and silk. They have found a way to coat fibres with titanium dioxide nano-crystals, which break down food and dirt in sunlight.
This team of academic researchers led by Walid Daoud, an organic chemist and non-material’s researcher, have made natural fibres such as wool, silk and hemp that will automatically remove food, grime, and even red-wine stains when exposed to sunlight. Apparently investigators are using sunlight as a complementary power resource to erase stains over these natural materials.
Monash University is not unique in developments with self-cleaning materials. Jeffrey Youngblood, engineering professor at Purdue University who is developing self-cleaning materials that repel oil said: ‘When you burn something, you oxidize. This titanium dioxide coating is just burning organic matter at room temperature in the presence of light’.
Walid Daoud and his colleagues coat the fibres with an invisible and very thin layer of titanium dioxide nanoparticles. This titanium dioxide, which is also used in sunscreens, toothpaste and paint, is a strong photocatalyst. In the presence of ultraviolet light and water vapor, it forms hydroxyl radicals, which oxidize, or decompose, organic matter. Moreover, Daoud says: ‘these nanocrystals cannot decompose wool and are harmless to skin’. Also, the coating does not change the look and feel of the fabric.
In the case of professionals and workers who use clothes of clear colours such as white and need to remain clean all the time it could be a very interesting breakthrough. The titanium dioxide is also capable of destroying diverse pathogens such as bacteria when exposed to the presence of sunlight, by breaking down the cell walls of the microorganisms.
The amazing result is that it should automatically make self-cleaning fabrics especially useful in hospitals and other medical settings. Daoud says that ‘self-cleaning property will become a standard feature of future textiles and other commonly used materials to maintain hygiene and prevent the spreading of pathogenic infection, particularly since pathogenic microorganisms can survive on textile surfaces for up to three months’.
The future of the textiles will be ruled by this kind of technology applied to clothes through nanoparticles applications, according to Daoud. He also argued that self-cleaning surely will become a standard feature not only in textiles but in other materials in order to maintain hygiene and prevent the spreading of pathogenic infection, particularly since pathogenic microorganisms can survive on textile surfaces for up to three month. However, the application of titanium dioxide to make self cleaning is a not a brand new technology.
For instance, in paints and window glass, titanium dioxide powder is applied as a transparent coating. Daoud and his team use nanocrystals of titanium dioxide in order to create self-cleaning wool. These nanocrystals are four to five nanometers in size. In previous experiments the researchers have made self-cleaning cotton through coating this material directly with these nanocrystals. But in the case of wool, silk and hemp, it has proved more difficult.
The fibre of these materials is made of a protein named ‘keratin’ which does not have any reactive chemical groups on its surface to bind with titanium dioxide.
The next stage is going commercial
Talk about clothes which can be cleaned automatically when exposed to the sunlight is something many individual groups and companies will consume in order to reduce costs of washing these items. Many wool manufacturers are planning to evaluate more in-depth this technology. Daoud said: “We are expecting that self-cleaning wools will be available in the general market within two years, once sufficient laboratory and industrial trials have been completed.”
Furthermore the greater importance of this technology is that the general population will have the possibility to limit considerably the use of water, chemicals and even energy, thanks to the advantage of this nanotechnology breakthrough.
Rigorous industrial control is the most important step in the commercial development of these fabrics dedicated to self-cleaning technology. This also involves testing whether existing textile manufacturing equipment can be used appropriately and economically in their production.Hector Nicolas Suero, NanoVip