Nano-filter extends life of masks worn to avoid coronavirus

A research team in South Korea has developed a nano-filter that could extend the life of face masks being worn extensively because of coronavirus (Covid-19).

Prof Kim demonstrating recyclable nano-fibre filter for face masks (Image: KAIST)

Demand for face masks in South Korea has led to the nation’s government rationing them to two per person per week. The face masks most commonly used are disposable N94 and N95 types that were made for filtering up to 95 per cent of fine dust.


A KAIST (Korea Advanced Institute of Science and Technology) research has now developed a nano-filter that is claimed to maintain filtering efficiency, even after hand washing, through the development of proprietary technology that aligns nanofibres with a diameter of 100~500nm in orthogonal or unidirectional directions. The team believe the reusable nano-filtered face mask could help relieve the challenges arising from shortages of face masks.

Professor Il-Doo Kim's nano-fibre filtered mask is said to maintain its 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 South Korea’s Ministry of Food and Drug Safety to bring his product to market.

Professor Kim used an insulation block electrospinning process to manufacture orthogonal nanofibres by controlling the alignment of nanofibres. This structure can minimise delivering of the pressure toward the air filter and maximise the filtration efficiency, which is different from existing disposable masks without nano-fibres.

According to KAIST, existing masks also fail to maintain their air filtering function because their electrostatic function disappears when exposed to water. The nano-fibre design was proven to be water-resistant with more than 94 per cent filtering efficiency in 20 repeated bactericidal tests with ethanol. The nano-filter 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.

"We believe that this mask can be reusable for about a month even after washing in ethanol,” Professor Kim said in a statement. “The inner filter can also be replaced. We found that the mask filters out up to 80 per cent of 600nm particles even after undergoing a bending test more than 4,000 times."

In February Professor Kim established the Kim Il-Doo Research Institute, a start-up that currently produces 1,500 nano-filters per day.