High efficiency particulate air (HEPA) filters fabricated by stepwise growth with structural hierarchy

Abstract

As concerns on carbon emissions and air pollution are increasing, and necessity of containing airborne infectious agents due to acceleration of coronavirus, demand for high-performance air filters is increasing. Recently, air filters with high efficiency have been developed and commercialized using nanofibers made of polymer materials, but they are disposable that leads to massive environmental wastes. In addition, because of the requirement of antibacterial performance, composite material filters such as depositing copper particles on the surface of polymer fibers are being developed, causing recycling more difficult. In this study, a copper filter with a two-layer structure is developed using an electrodeposition. First, we improve air permeability by growing a copper microfiber with a diameter of 1-10 um, and confirm the increase of physical filtration efficiency by adding a copper nanofiber structure with a diameter of 100-200 nm. Furthermore, the network of the copper fibers is controlled and stability is enhanced by a post-processing such as a roll compression and heat treatment. It has been verified that the fabricated filter has high filter efficiency when applying low voltage of less than 10 V, and the filter performance is improved by optimizing the height of the two different layers.