  Passive filtering is a common strategy used to reduce airborne disease
transmission and particulate contaminants in buildings and individual covers.
The engineering of high-performance filters with relatively low flow resistance
but high virus- or particle-blocking efficiency is a nontrivial problem of
paramount relevance, as evidenced in the variety of industrial filtration
systems and the worldwide use of face masks. In this case, standard N95-level
covers have high virus-blocking efficiency, but they can cause breathing
discomfort. Next-generation industrial filters and masks should retain
sufficiently small droplets and aerosols while having low resistance. We
introduce a novel 3D printable particle filter inspired by animals' complex
nasal anatomy. Unlike standard random-media-based filters, the proposed concept
relies on equally spaced channels with tortuous airflow paths. These two
strategies induce distinct effects: a reduced resistance and a high likelihood
of particle trapping by altering their trajectories with tortuous paths and
induced local flow instability. The structures are tested for pressure drop and
particle filtering efficiency over a wide range of airflow rates. We have also
cross-validated the observed efficiency through numerical simulations. The
designed filters exhibit a lower pressure drop than the commercial mask and air
filters (N95, surgical, and high-efficiency particulate air (HEPA)). The
concept provides a new approach to developing scalable, flexible,
high-efficiency air filters for various engineering applications.
