The golden fleece—adding value to New Zealand wool

Professor Jim Johnston and Dr Fern Kelly’s new technique, developed in the School of Chemical and Physical Sciences means a new washable biomedical fabric.

Silver, which is antimicrobial, is often used in wound dressings and the coatings of biomedical materials. But attempts to include silver in washable fabrics—like hospital pyjamas or sports socks—have led to problems with silver leaching out of the fabric and into the environment where it can upset the operations of wastewater treatment plants.

A new technique, developed by Professor Jim Johnston, from the School of Chemical and Physical Sciences, with his former PhD student Dr Fern Kelly, has solved this problem by creating nanoparticles of silver and chemically binding them to wool fibres.

“We’ve utilised the chemistry of the fibre in a novel way so the nanosilver is strongly bound, does not wash or leach out and shows excellent antimicrobial properties,” says Professor Johnston.

To test the effectiveness of the silver-infused fabric against bacteria, Professor Johnston’s team worked with Dr David Ackerley, of the School of Biological Sciences, to inoculate nanosilver-treated fabrics with E. coli or Staphylococcus Aureus bacteria. After seven days they measured the reduction in the bacterial colonies. By comparing how different concentrations of silver affected the bacteria, they concluded that concentrations of silver down to a few parts per million were sufficient to kill 99 percent of the bacteria in seven days.

After developing the silver nanoparticle and chemical binding process for wool, Professor Johnston’s team is now extending the process to other natural fibres like hemp and linen and is also testing the technology on a range of wool-based upholstery textiles from New Zealand and the United Kingdom. The technology is “very economically attractive”, says Professor Johnston, and has potential for wide applications for upholstery fabrics for use in mass transport, movie theatres, hospital waiting rooms or “anywhere there are people”.

In a parallel project, he and former PhD student Dr Kerstin Lucas have prepared and bonded nanogold particles to merino wool, resulting in a range of colours that don’t wear out or wash out. Nanogold merino also has antimicrobial, antistatic and insecticide properties, making it appealing for use in luxury vehicle and yacht upholstery as well as for high fashion apparel, accessories, interior furnishings and premium carpets.

Professor Johnston, who has a background in sheep farming and owns a farm in Taranaki, likes to work at the interface between university and industry.

“I’ve always looked for ways you can use science to improve some particular natural resource or product,” he says.

Professor Johnston and his Victoria University team are now looking for investment capital to scale up production of nanogold merino and nanosilver fabrics known as Goldwool and Silvertex.