A model in a silk attire

New Delhi, Feb. 12: Gold embroidery on silk may raise its aesthetic appeal, but a bit of embedded silver may impart it anti-microbial activity, promising odour-free garments and healthier dressing.

Scientists at the Indian Institute of Technology, New Delhi, have developed a process to create anti-microbial silk using tiny particles of silver, extending to silk a technology currently applied on cotton and polyester.

In their experiments, Mohan Gulrajani and his colleagues bathed silk fabric with a solution of silver nanoparticles — each particle so small that 30,000 would fit on top of a pinhead — and produced fabric that can stifle the growth of microorganisms.

“The silver nanoparticles seep into the fabric and remain there as guardians against germs,” said Gulrajani, professor of textile technology at IIT Delhi.

The researchers believe the technology might allow the production of medical dressings, and a variety of garments from socks to ties and scarves to saris that resist microbes.

“Silver nanoparticles have been known for anti-microbial activity, but silk treated with this material is not a commercial product yet,” said Manisha Mathur, a senior scientist with the Synthetic and Art Silk Mills Research Association, Mumbai. “It might add value to the silk, but it will raise the cost, too,” she told The Telegraph.

Silver nanoparticle finishes for textiles are available from foreign manufacturers and are imported for use on polyester and cotton fabrics that go into premium garments, a textile scientist said.

“For silk, this technology is still in the laboratory,” Mathur said.

In November 2007, fibre scientists at Inha University in South Korea announced that they had introduced silver nanoparticles into non-woven silk for possible applications in medical dressings.

Gulrajani said the nanoparticles give a tinge of cream to the fabric, but there is no change in the silk’s texture or feel. This makes them more suited for use on coloured silk than on white fabric.

Silk fabric attracts microbes when stored for long periods of time. “In hot and humid environments, the microbial colonisation of silk fabric is a big problem,” Gulrajani said.

For consumers, silver nanoparticle-treated silk will hold the promise of longer-lasting garments that don’t emit odour after use. And exporters would be able to maintain silk stocks longer, he said.

In a report published in the Journal of Applied Polymer Science, the IIT researchers said silk fabrics treated with 60 parts per million of this silver showed 100 per cent anti-microbial activity against a common bacteria named Staphylococcus aureus found on human skin, nose and throat, among other areas.

Fabric exporters caution that price will influence acceptance of the technology. “Textiles are highly price sensitive,” said Hemant Gupta, a partner with a Calcutta-based company exporting silk.

“Silk from India is not competitive because of cheap Chinese silk,” Gupta said. “But if we can add some value through anti-microbial properties, it may help the industry.”

Gulrajani said the increase in cost of anti-microbial silk was expected to be only marginal. The advantage of nanoparticles is that very small amounts can be spread over a large surface area.

“Just 20gm of silver nanoparticles can be spread over a football field,” Gulrajani said. However, he said, commercialisation of the technology would also depend on the size of the market.

Mathur also pointed out that process efficiency typically dropped when a textile technology is moved from the laboratory to an industry-scale plant.