The face masks most commonly used are disposable ones, originally made for filtering out up to 94 or 95 percent of fine dust, referred to as N94 or N95 masks.
A KAIST research team has developed a nano-filter that maintains excellent filtering efficiency even after hand washing through the development of proprietary technology that aligns nanofibers with a diameter of 100~500 nm in orthogonal or unidirectional directions. This reusable nano-filtered face mask could help to relieve the challenges arising from the supply shortage of face masks.
Professor Il-Doo Kim’s nano-fiber filtered mask will maintain its sturdy frame and filtering function even after being washed more than 20 times. Professor Kim, who has continued to study the filtering of fine dust using nano-filters, is now awaiting final approval from the Ministry of Food and Drug Safety to bring his product to the market.
Professor Kim used an insulation block electrospinning process to manufacture orthogonal nanofibers by controlling the alignment of nanofibers. This structure can minimize delivering of the pressure toward the air filter and maximize the filtration efficiency, which is different from existing disposable masks without nano-fibers. Existing masks also fail to maintain their air filtering function because their electrostatic function disappears when exposed to water. Thus, their filtering efficiency is reduced significantly, making it almost impossible to reuse them. However, this nano-fiber design was proven to be water resistant with more than 94% filtering efficiency in 20 repeated bactericidal tests with ethanol. The nano-fiber mask also showed no deformation in its nano-membrane structure despite the 20 hand washes. In particular, it was confirmed that there were no deformations in the membrane, even after soaking in ethanol more than three hours.
Professor Kim said, “We believe that this mask can be reusable for about a month even after washing in ethanol. The inner filter can also be replaced.” He added, “We found that the mask filters out up to 80 percent of 600-nanometer particles even after undergoing a bending test more than 4,000 times.” Professor Kim established his startup company, the “Kim Il-Doo Research Institute,” last February. It can currently produce 1,500 nano-fiber filters per day. https://www.youtube.com/watch?v=qwSncZVslJY
Researchers at The Hong Kong Polytechnic University have developed an electrostatically charged nanofiber filter that is able to filter nano-aerosols as small as 100nm. The team utilized polyvinylidene fluoride (PVDF) – an inert semi-crystalline thermoplastic often used in electrical insulation – to create nanofiber filters. Aerosol capture was improved by electrostatically charging the nanofibers, thereby increasing electrical interaction with aerosols in close range. The charged nanofiber filter demonstrated greater filtration efficiency for 100nm particles in comparison with a non-charged PVDF nanofiber filter – 54% vs 17%, respectively.
Iran’s Vice President for Science and Technology Sorena Sattari has announced the country is producing 400,000 nano-filters per day for N95 hospital masks amid the coronavirus pandemic.
The nano-filters are being developed by an Iranian company Nano Scale Technologists, and their capacity will soon multiply.
LIGC Applications has developed the Guardian G-Volt, a face mask with a graphene filtration system that can be sterilised and safely re-used. With its graphene filtration system the Guardian G-Volt is 99 per cent effective against particles over 0.3 micrometers, and 80 per cent effective against anything smaller, claims LIGC Applications.
For comparison, a N95 respirator mask blocks 95 per cent of particles over 0.3 micrometers. Viruses such as coronavirus can be transmitted through tiny droplets of water.
A low level electrical charge will pass through Guardian G-Volt when it is plugged in to a portable battery pack via a USB port. This charge would repel any particles trapped in the graphene mask. At home, a docking system will allow the mask to be fully sterilised so it can be worn again. The graphene in the mask is laser-induced graphene, a microporous conductive foam that can trap bacteria and conduct the electricity needed to sterilise the mask’s surface. It can then be heated and sterilised in the at-home dock. Wearing the mask can also protect against breathing in air pollution.
Czech company Respilon has developed a facemask that actively works to capture and kill viruses. The product incorporates both a nanofiber weave, which is small enough to prevent the entry of pathogens, along with a layer of copper oxide nanoparticles that actively kill viruses including the coronavirus when it comes into contact with them. Respilon has collaborates with an Israeli partner that developed the copper dioxide nanoparticles in order to produce the masks. “Thanks to the combination of nanofibers with copper oxide, it effectively protects against coronavirus,” Respilon director Roman Zima said. Further information at https://www.respilon.cz/