SARS-CoV-2 may spread through respiratory droplets released by infected individuals. The viruses are transmitted in moist droplets which cause coronavirus disease. Many countries have mandated the wearing of face masks, to various extents. However, the efficacy of masks is yet to be well rationalised given the limited microstructure information. Here, three common face masks and associated air permeations were revealed by coupling X-ray tomographic imaging and infrared thermal imaging techniques. Quantitative parameters have been extracted from the 3D images. Also, image-based modelling was performed to simulate the permeability to show how droplets pass through the porous structure. Our results show that the N95 mask has the smallest average pore diameter (~30 µm) and the densest nanoscale fibres which provides superior droplet filtration among all cases. Modifications to the N95 masks are proposed to develop the next generation mask with higher efficacy and better breathability.

SARS-CoV-2 可能通过感染者释放的呼吸道飞沫传播。病毒通过潮湿的飞沫传播，从而导致冠状病毒疾病。许多国家已在不同程度上强制要求戴口罩。然而，鉴于有限的微观结构信息，掩模的功效尚未得到很好的合理化。在这里，通过结合 X 射线断层扫描成像和红外热成像技术，揭示了三种常见的面罩和相关的空气渗透。已经从 3D 图像中提取了定量参数。此外，还进行了基于图像的建模以模拟渗透性，以显示液滴如何穿过多孔结构。我们的结果表明，N95 口罩具有最小的平均孔径（~30 µm）和最密集的纳米级纤维，可在所有情况下提供卓越的液滴过滤。建议对N95口罩进行改进，以开发出具有更高功效和更好透气性的下一代口罩。