AROUND the beginning of the 20th century the medical profession underwent an image makeover. Doctors swapped their traditional black coats for white ones, similar to those worn by scientists in laboratories. This was meant to bolster a physician’s scientific credibility at a time when many practising healers were quacks, charlatans and frauds. As the importance of antiseptics became more widely understood, white was also thought to have the advantage of showing any soiling.

Nowadays many doctors are likely to wear everyday clothes, or blue or green “scrubs”, which are said to reduce eye strain in brightly-lit operating theatres. White coats are reckoned to be capable of spreading diseases as easily as clothing of any other colour, especially when long sleeves brush against multiple surfaces. Many clinics and hospitals now have a “bare below the elbows” policy for staff, whether in uniform or their own clothes. This is also supposed to encourage more thorough handwashing.

What, though, if the clothes worn by medical staff could actively help prevent bugs being passed around? Some metals, such as gold and silver, have natural antibacterial properties and are used to coat certain solid items, such as medical implants. But putting metallic coatings onto stretchy and foldable fabrics is tricky, and those coatings can quickly be swept away in a washing machine. What is needed, reckons Liu Xuqing of the University of Manchester, in England, is a way to make antibacterial coatings for fabrics that, quite literally, hold tight.

Instead of gold or silver, Dr Liu’s metal of choice is copper. This exhibits the same bug-killing properties but has the benefit of being an awful lot cheaper than those two precious metals, making a commercial coating process easier to devise.

Working with colleagues from two Chinese institutions, Northwest Minzu University in Lanzhou and Southwest University in Chongqing, Dr Liu has been treating samples of fabric with a chemical process that grafts what is called a “polymer brush” onto their surfaces. As the name suggests, when viewed at a resolution of a few nanometres (billionths of a metre) through an electron microscope, the polymer strands look like tiny protruding bristles. That done they use a second chemical procedure to coat the bristles with a catalyst.

After this, they immerse the fabric in a copper-containing solution from which the catalyst causes the metal to precipitate and form tiny particles that anchor themselves to the polymer brush. Indeed, they bond so tightly that Dr Liu compares the resulting coating to reinforced concrete. Yet the process takes place at such a minute scale on the surface of the fabric that it should not affect the feel or quality of the finished material.

Dr Liu and his colleagues were able to use the process on both cotton and polyester. A test of the cotton samples for their antibacterial properties has shown that the new material is just as effective as silver, if not more so, at killing two bugs, Escherichia coli and Staphylococcus aureus, which can cause serious infections. The antibacterial effects were persistent, too. They survived more than 30 washes.

The chemistry involved, which is pretty straightforward, means the method should be reasonably easy to scale up. The researchers are already talking to firms about the possibilities of doing so. And work is continuing to improve the process and to treat the surfaces of other materials. Besides medical clothing, the coating might, for instance, be employed for garments worn in industries such as food processing, which need to avoid bacterial contamination.

Dr Liu is considering other uses for his invention, as well. One of his thoughts is to make conductive threads that could form part of electrical circuits woven into clothing. Such circuits might, for instance, link sensors that monitor the body. They might even carry current and signals to other fibres, treated to change colour in response, to produce fabrics that vary in hue and pattern—maybe to reflect, as detected by sensors, the wearer’s mood. A doctor could then have a coat of many colours.