Negative Voltage Electrospinning for the Production of Highly Efficient PVDF Filters

In recent years, the demand for filter media has increased dramatically, driven by the need to manufacture personal protective equipment and for various applications in the industrial and civil sectors. Nanofiber-based membranes are proposed as potential alternatives to commercial filtration devices. This study presents the design and implementation of an innovative pre-industrial electrospinning setup, combining a negatively charged spinneret and a positively charged counter-electrode, capable of producing polyvinylidene fluoride (PVDF) nanofibers with an average diameter of 410 nm and electrostatic surface potential values 3.7 times higher compared to a conventional electrospinning process, eliminating the need for further post-treatment. These properties are essential for improving mechanical and electrostatic filtration of small particles, including infectious droplets. The surface potential of the membranes is also long-lasting, as evidenced by tests one year after manufacture. As a case-study, these filters are used to manufacture surgical masks, reporting excellent performance in terms of bacterial filtration efficiency (BFE) up to 99.9%, and breathability (29.8±4.5 Pa cm⁻²) when compared to commercially available meltblown polypropylene (PP) face masks, and also complied with the stringent European standard (EN14683:2019) for type-II surgical masks. Furthermore, the pre-industrial setup allows for increased production capacity of up to 42 000 m² per year, suitable for large-scale production.