A team led by researchers from the University of Tokyo have successfully developed an inexpensive and easy method for applying a silver-based antimicrobial clear coating to new or existing textiles. Their coating combines silver with polyphenols and can treat a variety of textiles, with clothing able to be washed many times without losing its anti-odor properties.
As detailed in Scientific Reports [Richardson et al. Sci. Rep. (2022) DOI: 10.1038/s41598-022-05553-9], a polyphenol compound, tannic acid, was used to bind silver to fabrics. Although polyphenols are found in red wine and chocolate, and have a reputation for staining clothing and carpets, this new coating, called Ag/TA, is completely clear and doesn’t discolor textiles.
Led by Joseph Richardson and Hirotaka Ejima, the team devised two new ways to apply their antimicrobial coating in real-life situations. First, useful for commercial clothing or fabric producers, involved bathing textiles in a mixture of the silver compound and the polyphenol binder. The second method, more suited to the home, is to spray items of clothing, first with the silver compound and then with the polyphenol binder.
They focused on dipping and spraying as two simple processes regularly done in industry with fabrics and in the home for clothes. The binding power of TA is so strong that coated textiles such as cotton, polyester and even silk maintain antimicrobial and anti-odor properties for at least 10 washes.
The coating was assessed not just on odor-causing bacteria, but also on fungi and pathogens such as viruses, although this meant many more variables to control in testing variations of compounds. The coating was shown to neutralize everything it was tested on. A number of metals were screened, but silver was both effective and colorless, although other noble metals and monovalent metals could be incorporated into similar coatings in the future.
As Richardson told Materials Today, “The real significance is in the simplicity of the ingredients needed (just silver and polyphenols) and the ease of applying them to fabrics (dipping or spraying). There are other nice benefits like being colorless or lasting through the wash, but our true motivation was to make it so easy that anyone could do this in their own home.”
They have commercialized the technology through prototype spray bottles for odor protection, but hurdles remain before it’s approved for antimicrobial applications. The team also hope to try to make similar coatings for wearable electronics, as well as investigating other useful compounds polyphenols might help bind to fabrics.
“The real significance is in the simplicity of the ingredients needed (just silver and polyphenols) and the ease of applying them to fabrics (dipping or spraying). There are other nice benefits like being colorless or lasting through the wash, but our true motivation was to make it so easy that anyone could do this in their own home.”Joseph Richardson
Silver-based antimicrobial clear coating that cuts odors