Bioinspired interfacial adhesion toward next-generation air filtration
Air pollution ranks among the most severe environmental and global health challenges, with fine particulate matter (PM2.5) as a major concern. PM2.5 emissions primarily originate from human factors (e.g., industrial combustion, traffic exhaust, urban dust, biomass burning), alongside natural disasters (e.g., wildfires, volcanic eruptions, and dust storms) (Figure 1A). Besides its environmental impact, PM2.5 threatens public health by penetrating the alveoli and bloodstream, increasing the risks of respiratory and cardiovascular diseases. The World Health Organization aims to halve air pollution-related health impacts by 2040. Since 2015, high and high-middle sociodemographic index countries have reduced PM2.5-associated deaths by ∼19%, while other regions still account for ∼59% of global PM2.5-associated deaths.1 To alleviate these risks, membrane-based filters remain the principal approach to mitigate PM2.5 exposure but still face inadequate interfacial performance. Meantime, nature provides highly efficient and self-cleaning filtration systems. Inspired by these biological models, this commentary highlights how bioinspired control of interfacial adhesion can overcome long-standing challenges in air filtration by stabilizing particle capture and retention.
The filtration dilemma: Efficiency vs. pressure drop
A central challenge in membrane-based filters is balancing filtration efficiency (FE) and pressure drop (ΔP). Improving FE involves enhancing particle capture through interception, Brownian diffusion, inertial impaction, and electrostatic deposition.2 However, these mechanisms primarily rely on nanometer-scale van der Waals force (Fvdw), which is short ranged and weak in particle adhesion, leading to reduced FE (Figure 1B). Moreover, the isotropic nature of Fvdw causes dendritic deposit buildup that clogs the filter’s pores. Correspondingly, ΔP rises due to increased effective thickness (teff) and narrowed airflow channels. Conventional solutions mainly adjust pore sizes, fiber density, or layer thickness to optimize either FE or ΔP at the expense of the other. Such an FE-ΔP trade-off hinders membrane-based filters, which require both strong particle adhesion (high FE) and long-term stability (low ΔP), especially for PM2.5 filters.
To tackle the FE-ΔP trade-off, recent advances shift particle capture from solid-solid to liquid-solid interactions. Membrane-based filters enhance capture by introducing surface-infused viscoelastic liquids. This liquid layer enables rapid wetting on contact particles, creating a meniscus that induces Laplace pressure and exerts surface tension. These effects generate μN-scale capillary force (Fc), up to three orders of magnitude stronger than Fvdw. Depending on the wetting state (e.g., particle-liquid contact angle [θ], filling angle [β]), captured particles can be pulled into the liquid, improving surface adhesion and FE.
