London, November 25 : Swiss chemists have developed a new material from polyester fibres coated with millions of tiny silicone filaments, which they claim is the most water-repellent clothing-appropriate material ever created.
Stefan Seeger, the University of Zurich researcher who led the creation of the waterproof material, has revealed that drops of water stay as spherical balls on top of the fabric, and a sheet of the material need only be tilted by two degrees from horizontal for them to roll off like marbles.
The researcher says that a jet of water goes off the fabric without leaving a trace.
He attributes the incredible water resistance of the material to a layer of silicone nanofilaments, which are highly chemically hydrophobic.
He further says that that effect gets strengthened by the spiky structure of the 40-nanometre-wide filaments, which creates a coating that prevents water droplets from soaking through the coating to the polyester fibres underneath.
"The combination of the hydrophobic surface chemistry and the nanostructure of the coating results in the super-hydrophobic effect. The water comes to rest on the top of the nanofilaments like a fakir sitting on a bed of nails," New Scientist magazine quoted Seeger as saying.
The silicone nanofilaments also trap a layer of air between them to create a permanent air layer, known as plastrons, which ensures that water never comes into contact with the polyester fabric.
Seeger claims that the fabric would remain dry to the touch even when it is submerged in water for two months.
According to him, preliminary experiments have shown that the plastron layer can reduce drag when moving from water by up to 20 per cent.
"This could be very interesting for athletic swimwear applications," he suggests, raising the possibility of future swimsuits that never get wet.
The process to create the new coating involves just one step, in which silicone in gas form condenses onto the fibres to form nanofilaments.
The researchers say that the coating can also be added to other textiles, including wool, viscose and cotton, although polyester currently gives the best results.
They have even revealed that the new coating is durable, and unlike some water-resistant coatings, it remains more-or-less intact when the fabric is rubbed vigorously.
However, it did not survive an everyday washing machine cycle during tests.
"Although the textiles did show some degradation in the mechanical abrasion tests, their performance was very impressive. The era of self-cleaning clothes may be closer than we think," Steven Bell, director of the Innovative Molecular Materials Group at Queen's University Belfast, said.
A research article on this work has been published in the journal Advanced Functional Materials.