Innovation

Can we "trap and kill" germs Covid-19 before they get inside? Here's what we know.

Daniel Hambury - EMPICS/PA Images/Getty Images

Scientists around the world have been working day and night trying to fight coronavirus, with frustratingly meager results. Perhaps the greatest challenge remains transmission indoors, where tiny droplets can stay alive for hours. It's driven people out of activities ranging from going restaurants to watching hockey.

Hoping to win the indoor battle, a Texas-based team of researchers may have made a major breakthrough with a new “catch and kill” air filter that can trap and instantly kill coronavirus.

What's new — In a paper published online in Materials Today Physics earlier this month, researchers from the University of Houston and the University of Texas, collaborating with Texas-based medical real estate development firm Medistar and the Galveston National Laboratory, describe how they created what is a near-perfect coronavirus trap.

The team's coronavirus-killing air filter.University of Houston

“Considering that SARS-CoV-2 cannot tolerate temperatures above 70 °C, here we designed and fabricated efficient filters based on heated nickel (Ni) foam to catch and kill SARS-CoV-2," they write.

Air filters are common enough daily items, familiar to anyone who has ever used an air conditioner on a hot summer’s day. Typically made of aluminum or fiberglass, commercial filters are designed to catch pet danger, cigarette smoke, smog, pollen, and even bacteria. But, the scientists write, they “cannot effectively catch and kill the virus contained in aerosols (generally smaller than 5 micrometers [0.000196 inches] in size) or other airborne highly infectious agents, such as anthrax spores.” That includes coronavirus.

If a filter were to be an effective weapon against coronavirus and Covid-19, the researchers write, it would be “self-heated rather than have an external heat source,” since an external power source would likely raise temperatures in the surrounding area. So they decided to seek out material with electric conductivity, strong mechanical properties, and enough flexibility to be easily molded into different shapes.

What they did differently — They settled on nickel, which when converted into foam has a large, porous surface — perfect for trapping particles that are dispersed throughout an environment due to what are known as Van Der Waals forces.

How Van der Waals forces works. This natural phenomena, which also affects how rain droplets form, can make airborne viruses particularly tough to catch.Shutterstock

A nickel-based filter would have “the additional advantage” of localized heating, the authors write, which would limit the time the air spends within the filter.

All of that leads the scientists to determine that “Ni foam may act as a good filter for catching and killing SARS-CoV-2 or anthrax spores in air-conditioning systems.”

Other uses for this new type of foam — Such a filter could have a host of uses in wide society, says co-author Zhifeng Ren, director of the Texas Center for Superconductivity at the University of Houston, speaking in a press statement. “This filter could be useful in airports and in airplanes, in office buildings, schools and cruise ships to stop the spread of Covid-19. Its ability to help control the spread of the virus could be very useful for society.”

The system could be installed into conventional heating, ventilation, or air conditioning (HVAC) systems.

Why it's not so easy — The team found it “extremely challenging to design such a filter.” That’s because of a property known as electric resistivity, which is the opposite of conductivity: how strongly a material can resist an electric current.

Its strong resistivity made it difficult to achieve temperatures high enough to kill coronavirus. But eventually, using multiple pieces of folded nickel foam, they were able to reach 250 °C, and found an “almost 100 percent ability to catch and kill aerosolized SARS-CoV-2.”

There are further challenges in building such a filter en masse, particularly the price. Dwindling nickel ore supplies around the world have sent nickel prices rising throughout the global pandemic, especially since some mines have shut down in efforts to halt the highly contagious virus. Current nickel prices roam around $13,280 per pound, far more than gold.

Prices aside, the Texas team has high hopes. First co-author Dr. Faisal Cheema says in the team’s press statement that this air filter “will be on the forefront of technologies available to combat the current pandemic and any future airborne biothreats in indoor environments.”

What's next — Not content with the academic studies, the team hopes to quickly get their filters into the public, according to the press release, “beginning with high-priority venues, where essential workers are at elevated risk of exposure (particularly schools, hospitals and health care facilities, as well as public transit environs such as airplanes).”

Abstract: Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via air-conditioning systems poses a significant threat for the continued escalation of the current coronavirus disease (COVID-19) pandemic. Considering that SARS-CoV-2 cannot tolerate temperatures above 70 °C, here we designed and fabricated efficient filters based on heated nickel (Ni) foam to catch and kill SARS-CoV-2. Virus test results revealed that 99.8 percetn of the aerosolized SARS-CoV-2 was caught and killed by a single pass through a novel Ni-foam–based filter when heated up to 200 °C. In addition, the same filter was also used to catch and kill 99.9 percent of Bacillus anthracis, an airborne spore. This study paves the way for preventing transmission of SARS-CoV-2 and other highly infectious airborne agents in closed environments.
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