A titanate nanowire mask that can eliminate pathogens

‘Paper’ filter made from titanium oxide nanowires is capable of capturing pathogens and destroying them with light. This discovery by an EPFL laboratory could be used in personal protective equipment as well as in ventilation and air conditioning systems.

As part of efforts to curb the COVID-19 pandemic, paper masks are becoming increasingly mandatory. Their relative effectiveness is no longer in question, but their widespread use has a number of disadvantages. These include the environmental impact of disposable masks made from layers of nonwoven polypropylene plastic microfiber. Moreover, they simply capture pathogens instead of destroying them. “In a hospital setting, these masks are placed in special bins and treated appropriately,” says László Forró, head of EPFL’s Laboratory of Physics or Complex Matter. “Their use in the wider world – where they are thrown in open bins and even left on the street – can turn them into new sources of contamination.”

Researchers in Forró’s laboratory are working on a promising solution to this problem: a membrane made of titanium oxide nanowires, similar in appearance to filter paper but with antibacterial and antiviral properties.

Their material works by using the photocatalytic properties of titanium dioxide. When exposed to ultraviolet radiation, the fibers convert resident flour into oxidizing agents such as hydrogen peroxide, which have the potential to destroy pathogens. “Since our filter is exceptionally good at absorbing moisture, it can trap droplets that carry viruses and bacteria,” says Forró. “This provides a favorable environment for the oxidation process, which is triggered by light.”

The work of the researchers appears in today Advanced functional materials, and includes experiments demonstrating the ability of the membrane to destroy E. coli, the reference bacterium in biomedical research, and DNA strands in a matter of seconds. Based on these results, the researchers claim – although this must be demonstrated experimentally – that the process would be equally successful on a wide range of viruses, including SARS-CoV-2.

Their article also states that the creation of such membranes would be possible on a large scale: the laboratory equipment alone can produce a maximum of 200 m² or filter paper per week, if sufficient for a maximum of 80,000 masks per month. Moreover, the masks could be sterilized and reused a thousand times. This would reduce deficiencies and substantially reduce the amount of waste generated by refused surgical masks. Finally, the manufacturing process, in which the titanite nanowires are calcined, makes them stable and prevents the risk of nanoparticles being overtaken by the user.

A startup called Swoxid is already preparing to move the technology out of the lab. “The membranes could also be used in air treatment applications such as ventilation and air conditioning systems, as well as in personal protective equipment,” says Endre Horváth, lead author and co-founder of the Swoxid article.