Tailoring bimodal protein fabrics for enhanced air filtration performance

Abstract

Natural material-based nanofiber air filters promise to minimize any adverse impacts on the environment after use, but the nanofiber structure causes poor airflow performance, i.e. high airflow resistance. Constructing bimodal structures reduces airflow resistance without compromising removal efficiency but has been rarely studied for natural nanofiber air filters. In this study, we fabricate bimodal protein fabric air filters and carefully tailor their bimodal structure to achieve higher removal efficiency with significantly lowered airflow resistance. The bimodal structures are generated by co-spinning of denatured zein protein in two solvent systems, via controlling the protein denaturation degree and fiber shape/size. The bimodal structures with bimodal diameter distributions are then carefully adjusted by varying the feed rates. It is revealed that a bimodal fabric shows an optimized filtration performance when the fiber diameters locate at 2.44 and 0.13 μm, reducing the airflow resistance by up to 56.47 Pa (from 84.97 Pa to 28.5 Pa) with a high PM2.5 removal efficiency of 98.43%. The bimodal fabric treated with TX-100 shows a further improved filtration performance of filtering PM0.3 of 97.01% and PM2.5 of 99.15% at an ultralow airflow resistance of 21.1 Pa. Moreover, the treated bimodal fabric presents better long-term performance and higher removal efficiency in a humid environment. This work develops a simple and viable method for fabricating and tailoring bimodal air filters made of abundant natural protein for broad applications.