The diagram shows how a chemical modulation layer “disinfects” the respiratory droplets of the face mask wearer. Photo credit: Northwestern University
The antiviral layer attacks respiratory droplets to make the mask wearer less contagious.
In the pandemic, people wear face masks to respect and protect others – not just to protect themselves, says a team at Northwestern University Researcher.
With this in mind, the researchers developed a new concept for a mask that should make the wearer less contagious. The central idea, supported by the National Science Foundation through a RAPID grant, is to modify mask fabric with antiviral chemicals that can disinfect exhaled, escaping breath droplets.
By simulating inhalation, exhalation, coughing, and sneezing in the laboratory, the researchers found that nonwovens, which are used in most masks, work well for demonstrating the concept. For example, a lint-free wipe with a fiber density of only 19% disinfected up to 82% by volume of the breath droplets that had escaped. Such substances do not make breathing difficult and the chemicals on the mask did not come off in simulated inhalation experiments.
The research will be published in the journal today (October 29, 2020) matter.
Importance of protecting others
“Masks are perhaps the most important piece of personal protective equipment (PPE) needed to fight a pandemic,” said Jiaxing Huang of the Northwest, who led the study. “We quickly realized that a mask not only protects the person wearing it, but also protects everything else from being exposed to the droplets (and germs) released by the wearer.
“Wearing masks seems pretty confusing as some people don’t think they need personal protection,” added Huang. “Maybe we should call it Public Health Equipment (PHE) instead of PPE.”
The optical microscope image (left) in reflection mode shows traces of drying of all the droplets collected on a polyaniline film, but only those that have been acid modified (right) are visible in transmission mode as they change the color of the underlying polyaniline film from blue to green. Scale bar: 200 microns. Photo credit: Northwestern University
Huang is a professor of materials science and engineering at the McCormick School of Engineering in the Northwest. PhD student Haiyue Huang and postdoctoral fellow Hun Park, both members of Huang’s laboratory, are co-first authors of the paper.
“When there is an outbreak of infectious respiratory disease, source control is most effective at preventing the virus from spreading,” said Haiyue Huang, a 2020 Ryan Fellowship winner. “After leaving the source, breath droplets become more diffuse and more difficult to control. ”
The goal and the results
Although masks can block or redirect exhaled breath droplets, many droplets (and their embedded viruses) still escape. From there, virus-laden droplets can infect another person directly or land on surfaces to indirectly infect others. Huang’s team wanted to chemically alter the escape droplets so that the viruses are inactivated more quickly.
To achieve this, Huang tried to design a mask fabric that: (1) does not make breathing difficult, (2) molecular antiviral agents such as acid and metal ions, which can easily dissolve in exiting droplets, and (3) contain no volatile chemicals or easily peelable materials that the wearer may inhale.
After several experiments, Huang and his team selected two well-known antiviral chemicals: phosphoric acid and copper salt. These non-volatile chemicals were appealing because neither of them can be vaporized and then potentially inhaled. And both create a local chemical environment that is unfavorable for viruses.
“Virus structures are actually very delicate and ‘brittle’,” said Huang. “When part of the virus fails, it loses its ability to infect.”
Huang’s team grew a layer of a conductive polymer polyaniline on the surface of the mask fabric fibers. The material adheres strongly to the fibers and serves as a reservoir for acid and copper salts. The researchers found that even loose fabrics with a fiber packing density of around 11%, such as B. medical gauze, 28% of exhaled breath droplets changed by volume. For narrow fabrics, such as B. lint-free wipes (the type of cloth normally used for cleaning in the laboratory), 82% of the breath droplets were modified.
Huang hopes the current work provides a scientific basis for other researchers, particularly in other parts of the world, to develop their own versions of this chemical modulation strategy and further test it on virus samples or even on patients.
“Our research has become an open knowledge, and we will love it when more people join this effort to develop tools to empower public health responses,” Huang said. “Most of the work is done in the laboratory when the campus is closed. We hope to show researchers on the non-biological side of science and technology and those without many resources or connections that they can bring their energy and talent to the table. ”
Reference: October 29, 2020, matter.
This work was supported primarily by the National Science Foundation (RAPID DMR-2026944).
