Researchers from the University of Houston, in collaboration with others, have designed a “catch and kill” air filter that can trap the virus responsible for COVID-19, killing it instantly.
Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH), collaborated with Monzer Hourani, CEO of Medistar, a Houston-based medical real estate development firm, and other researchers to design the filter.
The researchers reported that virus tests at the Galveston National Laboratory found 99.8% of SARS-CoV-2, the virus that causes COVID-19, was killed in a single pass through a filter made from commercially available nickel foam heated to 200˚C, or about 392˚F. It also killed 99.9% of anthrax spores in testing at the national lab, run by the University of Texas Medical Branch.
“This filter could be useful in airports and in airplanes, in office buildings, schools and cruise ships to stop the spread of COVID-19,” Ren says. “Its ability to control the spread of the virus could be very useful for society.”
Medistar executives are also proposing a desk-top model, capable of purifying the air in an office worker's immediate surroundings.
TcSUH was approached by Medistar on March 31, as the pandemic was spreading throughout the United States, for help in developing the concept of a virus-trapping air filter.
The researchers knew the virus could remain in the air for about three hours. With businesses reopening, controlling the spread in air-conditioned spaces was urgent.
Medistar knew the virus couldn't survive temperatures above 70˚C (158˚F), so the researchers decided to use a heated filter. By making the filter temperature far hotter – about 200˚C – they were able to kill the virus almost instantly.
Using nickel foam met several key requirements – it’s porous, electrically conductive, and flexible, making air flow and heating possible.
But nickel foam has low resistivity, making it difficult to raise the temperature high enough to kill the virus. The researchers solved this problem by folding the foam and connecting multiple compartments with electrical wires. This increased the resistance enough to raise the temperature as high as 250˚C.
By making the filter electrically heated, rather than heating it from an external source, the researchers minimized the amount of heat that escaped from the filter, allowing air conditioning to function with minimal strain.
A prototype was built by a local workshop and tested at Ren's lab for the relationship between voltage/current and temperature. It then went to the Galveston lab to be tested for its ability to kill the virus. The filter satisfies requirements for conventional heating, ventilation, and air conditioning (HVAC) systems.“This biodefense indoor air protection technology offers first-in-line prevention against environmentally mediated transmission of airborne SARS-CoV-2 and will be on the forefront of technologies available to combat the current pandemic and any future airborne biothreats in indoor environments," says Dr. Cheema of UH College of Medicine.