Innovation in air filtration devices using advanced salt recrystallization techniques

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Electrically charged filters are widely used in air filtration devices and personal protective measures against airborne contaminants. However, electrical charge decay and hydrophobic nature of the filter fibers raise a concern over their performance against bioaerosols. As a result, the biological contaminants such as bacteria captured on filters can survive for many days, posing an immediate danger to public safety due to cross-infection, new aerosol release, and contaminated waste. Therefore, it is critical to develop an innovative mechanism to increase the performance of existing filtration devices against bioaerosols and apply the concept to fabricate new filtration devices capable of inactivating bacteria swiftly. ******We aim to develop a simple yet efficient antibacterial filter device, utilizing polypropylene (PP) fibers and salt recrystallization phenomenon. Salt-coated air filters can be designed not only to prevent transmission of bioaerosols but to physically destroy them. Specifically, when the bacteria-laden aerosols make contact with the filter fibers, the salt coating dissolves and then salt recrystallizes as aerosols evaporate. This causes inactivation of the bacteria through denaturation of antigens and/or destruction of lipid envelopes. In this program, we will be primarily dedicated to the design, development, and performance testing of the salt-coated PP filters. A salt coating will be formed by soaking or spraying the PP filters with a saline formulation, followed by drying. The thickness and morphology of the coated salt crystals will be controlled by varying salt concentration and drying method. The salt coating will be optimized to meet diverse application-specific requirements. For example, stability at different humidity conditions and substrate types will be improved by varying salt types and surfactants, respectively. We will evaluate the performance of the prototype air filters against regulatory agency standards by measuring pressure drop, filtration efficiency, time-dependent infectivity change, strain non-specificity, environmental stability, and reusability. ******The technological outcomes of this program will advance the general strategy to protect the Canadians and the world against bioaerosols. This in turn will contribute to the Canadian economy by expanding research outcomes to the industries specializing in personal/public protective measures (i.e. cabin air and HVAC filters, facial masks, and respirators), and promoting technology transfer to industrial partners. Ultimately, this program will lead to the multidisciplinary training of highly qualified personnel in advanced materials science, filter fabrication/surface modification techniques, and biotechnology, and bring Canada to the forefront of the universal search of an efficient air filtration device against bacterial pollution.