Engineering antimicrobial textiles is challenging due to discoloration issues and inhibited breathability. The process also includes harmful or harsh reagents and synthesis conditions and complex and/or time-consuming processing.
Scientists from the University of Tokyo‘s Graduate School of Engineering have pioneered applying a silver-based antimicrobial clear coating to new or existing textiles. Dubbed Ag/TA, the coating is cost-effective, simple, and has valuable implications.
The method uses polyphenols tannic acid (TA) explicitly to bind silver (Ag) to fabrics. Polyphenols are commonly found in food items and are notorious for staining clothes, such as wine and chocolate. Fortunately, the coating is completely clear, so it doesn’t discolor textiles, but best of all, it can survive being washed.
Postdoctoral fellow Joseph Richardson said, “As kids often do, my son stained his shirt with chocolate one day, and I couldn’t scrub it out. Associate Professor Hirotaka Ejima and I have studied polyphenols for over a decade, but this chocolate incident got me thinking about using tannic acid to bind silver to fabrics. We think we’ve found two methods to apply our antimicrobial silver coating to textiles, suitable for different use cases.”
“The first method might be useful for commercial clothing or fabric producers. Textiles can be bathed in a mixture of the silver compound and the polyphenol binder. Another method, perhaps more suited to small-scale settings, including the home, is to spray clothing items, first with the silver compound and then with the polyphenol binder. An obvious advantage is that people can add the coating to existing items of clothing.”
“But what’s most exciting is not the ease of application, but how effective the coating is. We wanted to study the effect of the antimicrobial coating not just on odor-causing bacteria but also on fungi and pathogens like viruses. With so many variables to control, it was a challenge of time and complexity to test variations of compounds against variations of microorganisms. But through carefully optimizing our testing methods, we found that the coating neutralizes everything we tested it on. So Ag/TA could be useful in hospitals and other ideally sterile environments.”
The coating demonstrated good antimicrobial and anti-odor properties for at least ten washes when tested.
Richardson said, “This isn’t just a hypothetical situation limited to the lab, I’ve tried it on my shirts, socks, shoes, even my bathmat. We’d like to see what other useful compounds polyphenols might help bind to fabrics. Antimicrobial silver might be the start.”