The coronavirus pandemic has prompted an unprecedented surge in demand for surgical masks, which offer some protection against the transmission of disease. However, masks become contaminated themselves as they filter pathogens from the air. As a result, they risk spreading more disease. That’s a design flaw researchers are currently trying to fix. They're working to design a better mask—one that can kill viruses and bacteria, rather than just trap them.

“Current masks don’t destroy the virus, that’s why they’ve been recommended for single use, but practically it is impossible to change the mask every few hours,” said Choi Hyo-jick, an assistant professor in the Department of Chemical and Materials Engineering at the University of Alberta. Choi has been working on a product that can provide an anti-viral coating to surgical masks to make them safer. The secret ingredient is salt.

“We treated the surface of the mask filters with salt crystal, so it’s not the fine salt powder that the public thinks it is,” Choi said. The coating works by first absorbing the water droplets that normally carry viruses and other pathogens through the air. When the water evaporates, it brings the virus into contact with the salt crystals, which punctures the viral cell’s membrane and destroys the virus.

Hoi first demonstrated the technique in 2017 but only in a lab setting using a mask with one layer. A standard surgical mask has three layers, with the inner layer working as an air filter while the two sandwiching layers offer water resistance and comfort.

Choi says when he first spoke to manufacturers in 2017, they weren’t interested in making masks safer but wanted to make them more comfortable instead. Choi’s latest research offers to provide both, creating a mask that is breathable but efficient at filtering—killing viruses within five minutes.

A different crystal

Far across the Pacific in Hong Kong, where a run on surgical masks has prompted the government to subsidize local production, Master Dynamic—an engineering lab in the Hong Kong Science and Technology Park (HKSTP)—is investigating how to provide an anti-viral coating to surgical masks, too. But Master Dynamics using a different material: nano-diamonds.

“We can treat the nano-diamonds in different layers so that it can kill all spectrum of viruses,” said Master Dynamics CEO Tom Kong. According to Kong, nano-diamonds can be treated to carry a small electrical charge which, when in contact with a virus, denatures the cell membrane and kills the virus on contact.

Master Dynamics has used nano-diamonds in applications before, including as a binding agent for drug delivery. Coincidentally, Choi’s interest in salt as an anti-viral agent also began when he was researching an improved drug delivery system, using sugar crystals as a binding agent to create an edible vaccine. That project didn’t work because the sugar crystals destroyed the vaccine, but it inspired Choi to pursue the use of crystals as an anti-viral coating.

Choi estimates the salt application will add an additional cost price of 50 cents per mask. The team at Master Dynamics hasn’t finished pricing analysis yet, but Kong pushes back against the notion that diamonds are expensive.

“When people think about diamonds they are normally thinking about jewelry where the cost is at a premium. But we’re using industrial grade nano-diamonds, not jewelry -grade diamonds, so the cost is much cheaper,” Kong said.

Most of the world’s industrial grade diamonds, often used for grinding and cutting other materials, are created in Chinese labs. The diamonds need to be polished so they're sharp and cut so they're the right shape, Kong said, which creates diamond 'chips' that Master Dynamics can use as source material.

Kong believes the masks could also be reusable, as the charge on the nano-diamonds will last for months, but testing still needs to be done. According to a press release from Hong Kong-based real estate developer New World Development, which has invested $1.2 million in Master Dynamics’s research under the guidance of CEO Adrian Cheng, preliminary results are expected within the next four months. In Alberta, Choi’s project is further ahead, but even that could take 12 to 18 months before a viable product is on the market.

A hurdle to use

If and when a product is widely available, however, there’s no guarantee medical practitioners will embrace the new design. According to Yeung Kinglun, a professor in the department of chemical and biological engineering at Hong Kong University of Science and Technology (HKUST), the medical community is extremely conservative when it comes to adopting new products.

“In terms of protective gear there is guidance from the World Health Organization on what to medical professionals should adopt and often the WHO tends to be even more conservative because they have to make sure every country can access the recommended items,” Yeung says. Diamonds and salt might not make the grade.