Pathogenic bacteria are usually the culprits responsible for the spread of nosocomial infections, but there are other sources of disease in hospitals, including viruses, fungi, their spores, prions, and endotoxins produced by bacteria.
Existing methods and standards usually involve two filter beds being used within hospitals’ ventilation systems. These have to be replaced on a regular basis, and though these filters trap pathogens and some of their byproducts, they don’t always incapacitate them.
Now, researchers at Rice University have developed a graphene-based material that captures a variety of pathogens and applies substantial heat to deactivate them, meaning that they can no longer cause health problems.
The researchers used the novel laser-induced graphene (LIG) that was developed at Rice previously. It is a porous 3D material made by direct laser writing on carbon. It is a flexible foam and, like other graphenes, can conduct electricity. By running enough current through it, the LIG can be made to heat to at least 350 degrees Celsius (662 degrees Fahrenheit). At these temperatures, not only are bacteria killed, but endotoxins, spores, prions, and other airborne dangers to health are also deactivated. The heating doesn’t have to be continuous, and is only applied once in a while to kill whatever has built up over the new filter. It heats quickly and cools quickly as well, requires little electricity to operate, and doesn’t have to be changed nearly as often as current filters.
The new filters have already been tested using an existing commercial vacuum filtration system. After 90 hours of passing pathogens and their byproducts through the filter, the researchers found that all the living components had been killed and their byproducts completely inactivated. They even went as far as incubating the filters to see if anything remaining would grow. There was no growth of bacteria on the filters or anything else, as compared with LIG filters that were not electrified during testing.
LIG is made by heating a polyimide using a laser beam. To create an LIG filter, the researchers had to make the material tougher so that it can withstand air flowing through it. This was performed by adding graphene on both sides of the polyimide, leaving the polyimide intact so that it provides appropriate support. Applying different temperatures to the material with the laser results in a dense mesh of graphene fibers covering a more solid sheet beneath. The combination results in a tough material that can capture all sorts of tiny particles while allowing electricity to access and zap them.
Study in ACS Nano: Self-Sterilizing Laser-Induced Graphene Bacterial Air Filter