Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.
Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093, USA.
Sci Adv. 2021 Mar 5;7(10). doi: 10.1126/sciadv.abf0452. Print 2021 Mar.
Face masks prevent transmission of infectious respiratory diseases by blocking large droplets and aerosols during exhalation or inhalation. While three-layer masks are generally advised, many commonly available or makeshift masks contain single or double layers. Using carefully designed experiments involving high-speed imaging along with physics-based analysis, we show that high-momentum, large-sized (>250 micrometer) surrogate cough droplets can penetrate single- or double-layer mask material to a significant extent. The penetrated droplets can atomize into numerous much smaller (<100 micrometer) droplets, which could remain airborne for a significant time. The possibility of secondary atomization of high-momentum cough droplets by hydrodynamic focusing and extrusion through the microscale pores in the fibrous network of the single/double-layer mask material needs to be considered in determining mask efficacy. Three-layer masks can effectively block these droplets and thus could be ubiquitously used as a key tool against COVID-19 or similar respiratory diseases.
口罩通过在呼气或吸气时阻挡大飞沫和气溶胶来防止传染性呼吸道疾病的传播。虽然通常建议使用三层口罩，但许多常见的或临时制作的口罩只包含单层或双层。我们使用精心设计的实验，结合高速成像和基于物理的分析，表明高速、大尺寸（>250 微米）的替代咳嗽飞沫可以穿透单层或双层口罩材料到相当大的程度。穿透的飞沫会雾化成许多更小的（<100 微米）飞沫，这些飞沫可能会在空气中停留相当长的时间。在确定口罩的效果时，需要考虑高速咳嗽飞沫通过流体动力聚焦和通过单层/双层口罩材料的纤维网络中的微尺度孔隙挤出而发生二次雾化的可能性。三层口罩可以有效地阻挡这些飞沫，因此可以广泛用作对抗 COVID-19 或类似呼吸道疾病的关键工具。
