Pure metallic nanofibrillar membrane for high-performance electrostatic air filtration with antimicrobial and reusable characteristics

Air filters have evolved to satisfy the demand for higher air quality in various industries over the decades. The common meltblown polymeric filters have a short lifetime due to charge loss, resulting in massive disposal. Recent composite filters based on metal deposition techniques enable semi-permanent collection of particulates via externally driven electrical charges, yet their use is limited by weak adhesion of metal coatings and extremely high operation voltages. Here, we introduce a thin nanofibrillar membrane composed of pure copper with high mechanical robustness, semi-permanent electrical filtration capability operating at low voltage, and reusability after wet-cleaning. We fabricate the structurally hierarchical large-area porous sheets via scalable electrodeposition of copper dendrites having 100-500 nm diameter on a woven microfiber mesh, followed by roll compression and thermal sintering. Geometric factors such as fiber diameter, porosity and thickness of the fibrillar network are precisely controlled during the fabrication steps guided by theoretical models, which determine the physical filtration efficiency and air permeability. The nano-percolated network can physically capture large dust particles, while its high conductivity enables dramatic improvement of filtration efficiency for small particulate matter via electrostatic attraction, resulting in 99.9% removal of 0.3 & mu;m particles with an applied voltage of 5 V. Less than 1% of nano copper fibers drop off during the peel-off test, validating the sufficient robustness of the fabricated nanoporous membrane, and wet cleaning approaches confirm its reusability with proper cleaning methods. Our new copper filter also exhibits excellent antimicrobial behavior which differentiates with conventional polymeric filters, expanding its use for protecting individuals from infectious disease.