The breakout of the Wuhan virus and serious influenza during the winter months in Hong Kong has raised concerns from the general public. Face masks are worn generally for the prevention of spread of virus and bacteria that cause sickness. Yet, misconceptions about the proper usage of face masks are very common in the community. Ir. Professor Wallace Leung Woon-Fong, Chair Professor of Innovative Products and Technologies of the Department of Mechanical Engineering, who has been studying the science behind masks and developing various combating technologies, suggested a user-friendly way to wear a proper mask.

Leung pointed out that face masks are worn by general public and professionals for protection from airborne viruses spread through spit and mucous. Therefore, the outer layer of the mask is hydrophobic (i.e. hate water) so that ‘germs’ carried with water in the spit from others around would not come in contact with the user wearing the mask. On the other hand, the inside layer is hydrophilic (i.e. like water) which absorbs moisture, keeping the user comfortable. Based on the above understanding, he introduced a scientific method to distinguish the inside or outside layer of a face mask for the general public.

His method is to simply add water droplets onto the surface of the mask and observe if the droplet ‘rolls up’ similar to that on a waxed surface (moisture prevention layer), or the water droplet soaks into the mask surface (moisture absorbing surface). The moisture prevention layer should be worn outside while the moisture absorbing layer should be worn inside in contact with the wearer. It is also important to test both sides in pursuit of the functionality of the mask. If both surfaces have been tested to have the same property, there is no inside or outside layer to speak of. Therefore wearing the mask with either side is fine, but it is preferred to purchase a better functional face mask. On the other hand, if the two surfaces are different, wearing the mask inside out lead to trapping of viruses and bacteria in the mask, this increases the risk of contact viruses and bacteria.

Professor Leung  had developed electrostatically charged nanofiber filter with multiple separator layers. The novel PVDF nanofiber filter can capture pollutant particles that are below 100 nm in diameter. It demonstrates much better performance in breathability and filtration efficiency, compared with existing technologies and products, and has a longer shelf life in high humidity up to 90 days. The filter or face mask applying the innovation would be an ideal defense against virus, such as measles, SARS, and other unknown health-threatening viruses during an outbreak. This is because most viruses are negatively charged and the PVDF nanofiber mask is positively charged making virus capture more effective.

Media interview by Ming Pao

底層吸水 面層防水 戴錯口罩 病菌有「隙」可乘