Fight COVID-19: Nanofibrous face mask

Nanofiber-based

     multifunctional technique

Existing face masks mainly use melt-blown fibers as the core filter material.  But the lack of uniformity and functional durability of the material poses a critical challenge  to the removal of fine particulates including viruses and bioaerosols. 

To address the issue, our team uses the electrospinning technique to fabricate nanofibrous filters with improved uniformity and enhanced filtration capability. The novel filters consist of numerous nanofibers with diameters at the nanometer scale, which is much smaller than the melt-blown fibers at the micrometer scale. The filters possess high porosity (e.g., > 80%), which effectively reduces their air filtration resistance.

 

Sandwich-like structure

The interconnected nanofibrous network also ensures a high removal efficiency of air pollutants due to its fine structure and tailored surface chemistry. In the preliminary experiments, our team designed a novel sandwich-like structure, composed of two hydrophobic skin layers and an inner functional layer, to further enhance the mechanical strength and filtration performance of the filters. The skin layers consist of nanofibers with a large dimension (e.g., 800-1000 nm in diameter), which can provide sufficient mechanical strength. 

Meanwhile, their hydrophobic nature can effectively prevent the wetting and penetration of water and thus protect the inner functional layer. The inner layer consists of small nanofibers of 100-400 nm in diameter, whose fine filter pore size allows more effective capture and retention of air pollutants.

 

High removal efficiency

       of  2.5-µm particles

Air filtration results show that the novel nanofibrous filters have significantly higher removal efficiency for 0.3-, 2.5-, and 10-µm particles compared to that of single use face masks. For example, the nanofibrous filter can have a removal efficiency ≥ 90% for 0.3-μm particles while the single use face masks only have an efficiency < 50%. 

 

Simple ethanol rinsing and heat drying

To address the concern of secondary pollutions associated with single use masks, the team has designed the filters to be ethanol-washable to enable filter disinfection, regeneration, and reuse. After a simple ethanol rinsing and heat drying, the regenerated filters are shown to effectively maintain their filtration efficiency. This reusable feature means improved sustainability and reduced burden on the environment. Currently, the team is optimizing the functions of the nanofibrous filters and developing original product prototypes.

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