Water-soluble filters from ultra-thin polyvinylpirrolidone nanofibers

Water soluble nanofilters (NF) to be used in the collection of biological micro- and nano-aerosols were manufactured by electrospinning polyvinylpyrrolidone (PVP) solutions in different solvent mixtures and neutralizing the electrospun PVP nanofibers with a cloud of small counter-ions generated by electrospraying a volatile solvent. Nanofibers electrospun from 6.5% PVP solutions in 0.8/0.2 (w/w) ethanol/acetone, 0.8/0.2 ethanol/water, and 0.5/0.5 ethanol/dimethylformamide (DMFA) mixtures had major diameters of 255, 155, and 5 nm, respectively. NF electrospun from PVP solution in the ethanol/DMFA mixture were almost transparent, and had the mass and the resistance to airflow less by a factor of 2–3 compared to the NF of similar aerosol-capturing efficiency but manufactured from the PVP solution in the ethanol/water mixture. The filtration properties of these two types of NF for sub-micron and nanoaerosol particles were characterized at a face velocity of air up to 13 m/s. It was shown that deformation of nanomats by a pressure drop at high velocity resulted in decreased nanoaerosol penetration. It was demonstrated that NF attached to a household vacuum cleaner allowed aerosol to be collected at a flow rate of 0.4–0.7 m3/min and transferred into a liquid probe as small as 20 µL for further analysis.