Recently, with the increased attention to indoor air quality, antimicrobial air filtration techniques have been studied widely to inactivate hazardous airborne microorganisms effectively. In this study, we demonstrate herbal extract incorporated (HEI) nanofibers synthesized by an electrospinning technique and their application to antimicrobial air filtration. As an antimicrobial herbal material, an ethanolic extract of Sophora flavescens, which exhibits great antibacterial activity against pathogens, was mixed with the polymer solution for the electrospinning process. We measured various characteristics of the synthesized HEI nanofibers, such as fiber morphology, fiber size distribution, and thermal stability. For application of the electrospun HEI nanofibers, we made highly effective air filters with 99.99% filtration efficiency and 99.98% antimicrobial activity against Staphylococcus epidermidis. The pressure drop across the HEI nanofiber air filter was 4.75 mmH2O at a face air velocity of 1.79 cm/s. These results will facilitate the implementation of electrospun HEI nanofiber techniques to control air quality and protect against hazardous airborne microorganisms.

We report a novel microfluidic technique for sampling of aerosols into liquids. The two-phase fluid, sampling air and collecting liquid, forms a stratified flow in the curved microchannel. By passing fluids through the curved region, the particles are transferred from air into the liquid phase by the particle centrifugal and drag forces. This microfluidic-based aerosol-into-liquid sampling system, called the MicroSampler, is driven by particle inertial differences. To evaluate the physical particle collection efficiency of the MicroSampler, we used standard polystyrene-latex (PSL) particles ranging in size from 0.6 to 2.1 μm and measured particle concentrations upstream and downstream of the MicroSampler with an aerodynamic particle sizer. The cutoff diameter of particle collection was selected controlling the air flow velocity (microfluidic air flow of 0.6 L/min showed a particle collection efficiency of ∼98% at a particle diameter of 1 μm), and continuous enriched particle sampling was possible for real-time postprocessing application. With regard to biological collection efficiency, the MicroSampler showed superior microbial recovery (Staphylococcus epidermidis) compared to the conventional BioSampler technique. These results indicate that our MicroSampler can be used as a portable, cost-effective, simple, and continuous airborne microorganism collector for applications in real-time bioaerosol detection.

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