“Every drop that is effectively removed from the room air would eliminate a potential source of transmission”

Although plexiglass barriers seem to be everywhere these days – between grocery stores, around restaurant tables, and high above office cubicles – they are an imperfect solution to blocking the transmission of viruses.

Instead of catching virus-laden breath droplets and aerosols, plexiglass dividers only deflect the droplets so that they ricochet off but stay in the air. To improve the function of these protective barriers, researchers at Northwestern University have developed a new transparent material that can capture droplets and aerosols and effectively remove them from the air.

The material is a clear, viscous liquid that can be applied to any surface including plastic, glass, wood, metal, stainless steel, concrete, and textiles. When droplets collide with the coated surface, they adhere to it, are absorbed and dry out. The coating is also compatible with antiviral and antimicrobial materials so disinfectants such as copper can be added to the formula.

“Droplets are constantly colliding with internal surfaces,” said Jiaxing Huang of Northwestern, the study’s lead author. “At the moment, plexiglass partitions are different devices; they distract droplets. If a surface could actually capture droplets, every single droplet that was effectively removed from the indoor air would be a successful elimination of a potential source of transmission. “

The research will be published in the journal on Wednesday (June 16) Chem. In the study, the researchers found that the coated surfaces, even when they bombarded surfaces with aerosol droplets – in a concentration that is orders of magnitude higher than typical for an indoor environment – still absorbed three times more aerosol droplets than uncoated surfaces.

Huang is a professor of materials science and technology at the McCormick School of Engineering in Northwestern. Zhilong Yu, Murak Kadir, and Yihan Liu – all members of Huang’s laboratory – co-authored the paper. The team started this project during the stay-at-home order at the start of the pandemic.

The main component of the Northwestern team’s material is a polyelectrolyte polymer, which is widely used in a wide variety of cosmetic products. When applied with a blade or brush, the resulting formula produces even and conformal coatings on a variety of interior surfaces without damaging or discoloring the original material.

Huang’s team found that the surfaces remained transparent and opaque-free even when droplets were poured over them. In other words, the surfaces did not appear dirty or soiled after spraying with droplets. When used on Plexiglas barriers, these coated barriers would not have to be cleaned more frequently than uncoated barriers.

Most infectious diseases are transmitted through respiratory droplets and aerosols that humans constantly release when they speak, laugh, sing and exhale. Because the coating is so versatile, Huang envisions that it could be used on plexiglass barriers and face shields, as well as on non-contact or low-contact surfaces like walls or even curtains to remove these airborne droplets.

“There are huge areas of interior surfaces that people or pets barely touch. If we repurpose these “inactive” surfaces to catch breath droplets, they could become functional “devices” to reduce the airborne transmission of infectious diseases, ”he said. “Pathogens trapped on the surface can then be easily inactivated over time, which can be accelerated by applying disinfectants in advance. They can also be removed during routine cleaning. “

While Huang says face masks are an indispensable public health tool for preventing the spread of infectious droplets, he believes droplet trapping on surfaces could be another powerful tool.

“In a computer game, for example, you don’t want to go to a battlefield with just one armor,” he said. “It makes sense to use multiple layers of defense.”

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The study “Drip-catching coatings on environmental surfaces based on cosmetic ingredients” was supported by a JITRI-Northwestern Research Fellowship of the Jiangsu Industrial Technology Research Institute, which is administered by the Northwestern Initiative for Manufacturing Science and Innovation.

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