Nanofibrous aerosol sample filter substrates: Design, fabrication, and characterization

The manuscript demonstrates the application of nanofibrous filtration technology to aerosol sampling, by suggesting the fabrication sequence and laboratory validation of sampling filters. Four multilayer composite filters were developed from polymers Polyc[ε]aprolactone (PCL), Cellulose acetate (CA), Poly(1-acrylonitrile) (PAN), and Poly(hexano-6-lactam) (PA6) by two modifications of electrospinning process. The layered structure provided a fibre and pore gradient from the microfibrous base layer, the mesofibrous middle layer, and the nanofibrous upper layer, acting as a 2D collection surface for aerosol particles. The sampling filters were characterized for their morphology, wettability, weight stability, filtration efficiency, and pressure drop. The fibre diameter of the nanofibrous layer ranged from 0.42 ± 0.21 μm (PCL) to 0.086 ± 0.02 μm (PA6), while pore size ranged from 2.83 ± 0.35 μm (CA) to <0.4 μm (PA6). Such a morphology allowed for reaching a consistent particle collection efficiency ranging between 99.4 and 99.9% at a particle size of 0.3 μm, and at a reasonable pressure drop, such as 0.5–2.2 kPa at a face velocity of 10 cm/s. The fabrication sequence and obtained indicate a suitability for the preparation of bespoke filtering substrates to suit a specific subsequent physical, chemical, or toxicological analysis of collected particles.