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Tannic acid utilized to "stain" odor-eliminating silver onto clothing

By Ben Coxworth
February 08, 2022
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A diagram illustrating the antibacterial functionality of the colorless Ag/TA coating, which is less than 10 nanometers thick
Ejima et al
A diagram illustrating the antibacterial functionality of the colorless Ag/TA coating, which is less than 10 nanometers thick
Ejima et al

Red wine and chocolate are notorious for staining clothes, thanks to the tannic acid that they and other substances contain. Scientists at the University of Tokyo have now used that acid in a textile coating which keeps clothes from stinking, and that doesn't wash out.

Along with the tannic acid (which is a type of polyphenol), the ultra-thin coating also incorporates silver nanoparticles.

While silver is well known for its ability to kill odor-causing bacteria, researchers have previously had difficulty chemically binding it to fabric. This is an important consideration, not only because frequently reapplying a silver coating would be a hassle, but also because silver nanoparticles may pose a health hazard when released into the environment.

That's where the new Ag/TA (silver/tannic acid) coating comes in.

The tannic acid binds with both the silver and the fabric, keeping the two securely bound to one another. And although tannic acid does produce colored stains in large amounts, the coating itself is colorless. It could be applied to fabrics in either of two ways – textile manufacturers could dip sheets of material in an Ag/TA solution, or consumers could spray it onto items of clothing themselves.

In tests conducted so far on cotton, polyester and silk, the coating has proven to be highly effective at killing not only bacteria but also fungi and viruses. What's more, it has maintained that functionality for at least 10 wash cycles, plus the application of the coating didn't affect the materials' flexibility or breathability.

"This isn’t just a hypothetical situation limited to the lab, I’ve tried it on my own shirts, socks, shoes, even my bathmat," said postdoctoral fellow Joseph Richardson, who is leading the study along with Assoc. Prof. Hirotaka Ejima. "We’d like to see what other useful compounds polyphenols might help bind to fabrics. Antimicrobial silver might just be the start."

A paper on the research was recently published in the journal Scientific Reports.

Source: University of Tokyo

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Good ThinkingAntibacterialSilver InkTextileUniversity of TokyoCoatingsNew Atlas Audio
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Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.
3 comments
EH
10^-5 liters of 0.01% silver AgNO3 per square centimeter of cloth is what they used, which is about 3*10^-7 troy ounces silver per square meter, costing less than a thousandth of a cent for the silver over a square meter (if I've done the math right). The coating gives over 99.9% reduction in viruses, and over 99% for other organisms (bacteria, fungi), performing particularly well on silk, but also on paper. It can coat practically anything, but a porous or rough surface works best. It should work well in water and air filters, but also could see use anywhere you don't want microorganisms growing - building materials, furnishings, paper currency, packaging, as well as cloth.
Thornapple
NIce. Can someone now try getting deodorant ingredients into exterior house paint because absolutely nothing removes the stuff from clothing.
EH
That cost calculation was off, the silver cost per square meter is:
"10 microliter/ sq cm 0.1 percent g/cc sq m XAG -> cent"
8.5249318952342974
So a realistic cost would likely be $0.20 - $0.50 /sq m.
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