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Scientists develop coating that can capture airborne droplets

The transparent liquid coating can be painted onto plexiglass barriers, face shields or surfaces like wood and stainless steel

A file photo shows an El Capitan Theatre employee talking to a customer through a plexiglass window. This new material is a clear, viscous liquid that can be painted onto any surface, including plastic, glass, wood, metal, stainless steel, concrete and textiles. (Chris Pizzello/Invision/AP)

Latest scientific research suggests that airborne transmission of covid-19 is a significant concern. In May, the US Centers for Disease Control and Prevention (CDC) recognised that SARS-CoV-2, the virus that causes covid-19, is airborne and can be transmitted via fine droplets released during respiration.

Now, scientists at the Northwestern University in the US have developed a sticky wall coating that repurposes ingredients used in hair conditioners to trap aerosolized droplets, and hope it will become another tool in the fight against covid-19 and other airborne diseases and disease-causing pathogens.

The substance can be applied to surfaces such as plexiglass dividers to capture respiratory droplets, rather than allowing them to bounce off and remain in circulation, an AFP report explains.

Also read: Can antimicrobial surfaces work against the covid-19 virus?

"Droplets collide with indoor surfaces all the time," said Northwestern University engineering professor Jiaxing Huang, senior author of a paper on the subject that was published this week in the journal Chem.

"Right now, plexiglass dividers are deviating devices; they deflect droplets. If a surface could actually trap droplets, then every single droplet effectively removed from indoor air would be a successful elimination of a potential source of transmission," Huang explains in an official news release.

A vial of the polymer-based solution. Huang and his colleagues applied the substance with a brush to a variety of surfaces and performed tests to compare coated and uncoated surfaces.
A vial of the polymer-based solution. Huang and his colleagues applied the substance with a brush to a variety of surfaces and performed tests to compare coated and uncoated surfaces. (Courtesy: Northwestern University)

Covid-19 is primarily transmitted through respiratory fluids -- including large droplets and fine aerosols -- when an infected person speaks, sneezes or breathes. The main way to remove these from the air is to open windows, allowing adequate ventilation, and to use high-filtration devices that capture fine particles and change out the air at high rates.

To build extra protection on top of that, Huang and fellow researchers came up with the idea of using PAAm-DDA, a polymer which is commonly used in hair products and other cosmetics to lock in moisture, as the main ingredient of their coating.

They applied the substance with a brush to a variety of surfaces and performed tests to compare coated and uncoated surfaces. A coated plexiglass barrier captured nearly all aerosolized microdroplets, and 80 percent of large droplets, compared to a barrier that was uncoated.

A 3D image, taken with laser confocal microscopy, showing crater-like features generated by the captured droplets.
A 3D image, taken with laser confocal microscopy, showing crater-like features generated by the captured droplets. (Courtesy: Northwestern University)

The coating did not become visibly soiled after use, and the scientists said it would not require cleaning more often than non-coated barriers. Once saturated, the substance should be wiped down with water and reapplied.

Since it can be applied to a variety of surfaces, including concrete, metal and fabric, Huang said it could be used on low-touch areas such as walls or curtains to turn those into "functional devices" that would help capture aerosolized particles. Many more research steps are required to confirm the coating's utility before it can be authorized for use.

"We understood that the current pandemic may end before this concept is implemented," Huang said. "It may or may not be used now. But next time, when an outbreak like this happens, I think we will be better equipped."

(With inputs from AFP)

Also read: Covid is airborne, scientists say. Now authorities think so too

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