[Courtesy of KAIST]
SEOUL -- South Korean researchers have developed a recyclable mask using a nanofiber filter that maintains efficiency even after washing more than 20 times. Mass-production is possible if state approval comes.
The nanofiber filter mask was developed by a research team led by Kim Il-doo, a materials science and engineering professor at the state-funded Korea Advanced Institute of Science & Technology (KAIST). A nanofiber filter was placed inside a cotton mask.
When washed and reused with ethanol spray or soap 10 to 20 times per filter, two to three filters can be used for more than a month. "It can be reused with ethanol disinfection or light hand washing, so it can solve the lack of masks and an environmental problem," Kim said.
Kim's team used an "insulated block electro-radiation" method that intersects nanofiber crosswise or aligns it straight. The performance of masks depends on the efficiency of filters. Melt-blown (MB) filters, which are a net of finely spun-bonded polypropylene that collects microscopic matters, have been widely used.
MB filters are non-woven, randomly intertwined. The size of air holes is various, requiring multiple layers to block small particles. Because static electricity formed on the surface of an MB filter disappears when it touches moisture, efficiency decreases drastically after a certain period of time, or when it is washed.
Nanofiber filters are made by crossing fine nanofiber at right angles or by tightly aligning them in a row to create smaller air holes of the same size that allow blocking efficiency with thinner thickness than conventional filters. It is airy and easy to breathe.
Although Kim's team hand-washed the nanofiber filter more than 20 times with soap and dipped it in ethanol for more than three hours, its structure remained unchanged and maintained 94 percent of the original performance. Even after more than 4,000 times of repeated bending, it had a blocking effect.
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