Aerosol Filtration Efficiency Research Articles

Photo-responsive polypropylene/zinc oxide/polydopamine-TEMPO composite membranes with light-induced self-sterilization

Face masks play a pivotal role in preventing infection transmission. However, the capture of infection-sourced particles in face masks poses challenges related to reuse, necessitating proper disposal. We developed a self-sterilizable polypropylene-based membrane for face masks to address challenges associated with infection transmission prevention. The membrane, created using 3D printing, underwent functionalization with zinc oxide (ZnO) and polydopamine (PDA)-TEMPO to achieve broad-spectrum light absorption and facilitate self-sterilization through photocatalytic and photothermal effects upon light exposure. The hydrophobic surface (water contact angle: 133 ± 2 °) minimized moisture accumulation, and the membrane exhibited robust mechanical properties, including shear strength (1.25 ± 0.5 kPa) and peel resistance strength (112.8 ± 11.2 kPa). The evaluation demonstrated stability in airflow (0 to 500 cm3/s) and excellent aerosol filtration efficiency (94.8 ± 0.6 %) for particles (PM 0.3, PM 2.5, PM 10), comparable to commercial masks. The membrane showed antibacterial efficacy over five uses in a simulated respiratory environment. Safety assessments confirmed biocompatibility through cytocompatibility and skin irritation assays. In conclusion, this membrane offers efficient filtration and photo-triggered sterilization, presenting a promising solution for next-generation face masks to address concerns related to reuse, disposal, and infection control.

Quaternary ammonium salt coated air filter for bioaerosol removal from building indoor air

Developing air filters with biocidal ability is important to protect the public from infectious respiratory diseases. A simple spray-coating approach was devised to fabricate antimicrobial air filters to remove bioaerosols. The commercial antimicrobial agent Goldshield 75 was coated on the air filters through covalent immobilization, endowing the fabricated filter with long-lasting biocidal ability. All coated filters significantly inhibited both Gram-positive bacteria (Micrococcus luteus) and Gram-negative bacteria (Escherichia coli). The antibacterial ability of the coated filters is similar to the commercial AeraSafe antibacterial filter. The coated filter showed over 99.9 % antibacterial efficiency 3 months after the application of the coating. Both bacterial and virus filtration efficiencies of coated charged polypropylene filter were higher than 99.9 %. The coating did not have much effect on the NaCl aerosol filtration efficiency of the filters. This simple spray-coating strategy is a practical method for producing antimicrobial air filters for the prevention of infectious respiratory diseases.

Impact of common face mask regeneration processes on the structure, morphology and aerosol filtration efficiency of porous flat sheet polysulfone membranes fabricated via nonsolvent-induced phase separation (NIPS)

The potential of flat sheet polymeric membranes as a sustainable solution for reusable facemask filters was investigated by analyzing the effect of common face mask regeneration processes on polysulfone (PSf) membranes’ structure, morphology, and aerosol filtration efficiency. The impact of regeneration processes, such as isopropanol (IPA), detergent and bleach washes, and ultraviolet light exposure, was for the first time compared between surgical masks, N95 masks and flat sheet PSf membranes. The PSf membranes were fabricated via non-solvent induced phase separation (NIPS), and demonstrated a higher particulate filtration efficiency (99.06 ± 1.38%) for PM0.3 i.e., particulate matter of 0.3 µm aerodynamic diameter compared to surgical mask (70.93 ± 2.82%) and N95 (N95-1: 97.09 ± 7.37%; N95-2: 91.46 ± 1.45%). Scanning electron microscopy (SEM) analysis revealed no significant changes in morphology of treated membrane pores. Fourier transform infrared spectroscopy (FTIR), contact angle goniometry, and Xray photoelectron spectroscopy (XPS) analyses revealed retained membrane surface composition, hydrophobicity, and showed no residual elements from sterilizing chemicals after rinsing for 30 min. Statistically insignificant differences in treated and untreated PSf membrane pore size, porosity, and mechanical strength obtained in this work suggest the absence of chain scission due to radical formation, which can arise from polymer chains exposure to UV and bleach (NaClO), and change in polymer chain conformation. Treatment with IPA and detergent, which resulted in 46.7 ± 5.5% and 64.3 ± 12.9 % reduction of 0.3 µm aerosol filtration efficiency, respectively, for commercially available face masks, showed an insignificant decrease in PSf membrane filtration performance, which was attributed to dissipation of electrostatic charges responsible for the high filtration efficiency of non-woven face masks.

A dual-geometry pore-size-resolved model to predict deep-bed loading in a wall-flow filter

A gasoline particulate filter (GPF) is an effective wall-flow technology for gasoline engine particulate matter (PM) emission control via deep-bed filtration through porous ceramic walls within a honeycomb channel structure. An analytical filter model is desired to understand its efficiency and pressure drop under engine operating conditions and, thereby, reduce the development costs for meeting emission regulations and engine performance targets. Most existing models either oversimplify the filter geometry or do not offer good predictions in the soot loading regime. The present work treats the deep bed regime as two co-existing filters with different geometries based on their natural morphologies, one that describes the porous wall and the other for the fiber structure created by soot deposition. Both models are dynamic to account for changes in pore size distribution and soot dendrite growth during loading. Model validation by 12 sets of experimental filter loading data shows that it provides reasonable predictions of both filter efficiency and pressure drop during deep-bed loading for different GPF wall-flow filters under various operating conditions. Scanning electron microscopy (SEM) confirms model predictions for the unit collector size of the dendritic filter formed by soot deposition. Numerical simulation using GeoDict was also carried out to validate the model predictions on particle deposition location. The model is used to investigate the evolution of pore-size-resolved aerosol flow, filtration efficiency, mass loading, and particle packing density during loading. The impact of porosity, mean pore size, and pore size distribution on filter loading performance is studied. The results suggest that increasing porosity, narrowing pore size distribution, and increasing mean pore size can improve filter performance, offering pathways for future filter optimization.

Smart Face Masks for COVID-19 Pandemic Management: A Concise Review of Emerging Architectures, Challenges and Future Research Directions

Smart sensing technology has been playing tremendous roles in digital healthcare management over time with great impacts. Lately, smart sensing has awoken the world by the advent of smart face masks (SFMs) in the global fight against the deadly Coronavirus (Covid-19) pandemic. In turn, a number of research studies on innovative SFM architectures and designs are emerging. However, there is currently no study that has systematically been conducted to identify and comparatively analyze the emerging architectures and designs of SFMs, their contributions, socio-technological implications, and current challenges. In this article, we investigate the emerging SFMs in response to Covid-19 pandemic and provide a concise review of their key features and characteristics, design, smart technologies, and architectures. We also highlight and discuss the socio-technological opportunities posed by the use of SFMs and finally present directions for future research. Our findings reveal four key features that can be used to evaluate SFMs to include reusability, self-power generation ability, energy awareness and aerosol filtration efficiency. We discover that SFM has potential for effective use in human tracking, contact tracing, disease detection and diagnosis or in monitoring asymptotic populations in future pandemics. Some SFMs have also been carefully designed to provide comfort and safety when used by patients with other respiratory diseases or comorbidities. However, some identified challenges include standards and quality control, ethical, security and privacy concerns.

Coulombic force contribution to nano scale aerosol capture by a wire grid: Quantitative comparison of experiments and simulations

Fibers of filter media and aerosol particles both typically have some distributions of electric charge. Attractive coulombic interactions between charged particles and fibers enhance aerosol filtration efficiency; however, these coulombic interactions are difficult to characterize due to the complex, nonuniform fiber charge, diameter and spacing of typical filter media. We develop an experimental filter assembly to control these coulombic interactions. The filter assembly consists of three sequential electrically isolated metallic grids—high voltage is applied to the middle grid and the adjacent outer grids are electrically grounded such that the electric potential distribution in the filter assembly is well-defined. We test this filter assembly with aerosols of controlled diameter (ranging between ∼70 and 500 nm) and electric charge (1e−), and systematically increase the applied voltage to the middle grid to enhance coulombic interactions and consequently the filter efficiency. We develop particle trajectory simulations to model our experimental filter assembly such that all parameters in the simulation have direct basis from the experimental system. We find excellent quantitative agreement between the filter efficiency measured in experiments and predicted from simulations without any fitting parameters. The precise control and accurate simulation of coulombic interactions demonstrated in this study indicate that the experimental and simulation methodologies developed here may be applied to uncover fundamental insights into the role of coulombic forces in more complex phenomena such as filter clogging.

Mixture Aerosols Filtration on Filters with Wide Fibre Diameter Distribution - Comparison with Theoretical and Empirical Models

A methodology for calculating aerosol filtration efficiency using non-woven filters with polydispersity distribution of fibre diameters was formulated. In order to verify the results of the calculations experimentally, filters made of polypropylene non-woven fabric were used to filter solid (soot) and liquid (oil) aerosols and their mixtures with different concentrations. In order to increase the accuracy of the calculations, the division of the diameter distribution into several (1–100) ranges of values was considered. The influence of the number of these intervals for theoretical and empirical equations available in the literature was investigated. This effect was found to be significant, and replacing one diameter value representing all the fibres in the filter with twenty diameter ranges, each representing only a fraction of the total fibres, is sufficient to minimize the error due to the underrepresentation of the actual fibre distribution in the filter. Calculation of the mean particle size after the filter was performed using a set of theoretical and empirical equations. The calculations take into account the change in packing density, flow velocity and fibre diameter over time as a result of filling the filter with particles deposited on it. The obtained results were compared with the measurement results. It has been found that such changes in the monofilament performance model are insufficient to properly describe the effects inside the filter.

Evaluation of biocidal properties of biodegradable nanofiber filters and their use in face masks

ABSTRACT Due to the recent coronavirus-2019 pandemic, several studies have emerged looking for new materials, especially with biocidal characteristics. Thus, the present research investigates the antibacterial properties of biodegradable cellulose acetate (CA) / cetylpyridinium bromide (CPB) electrospun nanofibers, their aerosol filtration, and the possible use as a filter media of surgical face masks. Then, samples of these nanofibers were produced over a nonwoven substrate, using different volumes of polymeric solution during the electrospinning process. The evaluation of the antibacterial properties of the nanofibers was performed for Escherichia coli and Staphylococcus aureus using quantitative methods. The aerosol filtration performance was evaluated in these samples for NaCl nanoparticles (from 7-300 nm) and with 8 mL min−1 of air flow rate. The results show that the single use of the surfactant has antibacterial properties from a concentration of 39 µg mL−1 of solution. The nanofibers presented a reduction of 100% for both bacteria. Air filtration tests showed 126.03 and 207.73 Pa cm−² of pressure drops and 63 and 77% of aerosol filtration efficiency (FE) for samples with 0.13 and 0.15 mL, respectively. Regarding the nanofiber produced with 0.35 mL, the value obtained was 115.13 ± 33.64 Pa cm−2 and 3.15% of particle penetration. These breathability values are higher than those required for the surgical face mask standard, indicating that improvements in the porosity and thickness are necessary to meet the Brazilian requirements. However, the nanofibers could be applied as filter media for indoor air conditioning systems due to their FE and biocidal properties.

Standard hospital blanket warming cabinets can be utilized for complete moist heat SARS-CoV2 inactivation of contaminated N95 masks for re-use

Shortages of personal protective equipment for use during the SARS-CoV-2 pandemic continue to be an issue among health-care workers globally. Extended and repeated use of N95 filtering facepiece respirators without adequate decontamination is of particular concern. Although several methods to decontaminate and re-use these masks have been proposed, logistic or practical issues limit adoption of these techniques. In this study, we propose and validate the use of the application of moist heat (70 °C with humidity augmented by an open pan of water) applied by commonly available hospital (blanket) warming cabinets to decontaminate N95 masks. This report shows that a variety of N95 masks can be repeatedly decontaminated of SARS-CoV-2 over 6 h moist heat exposure without compromise of their filtering function as assessed by standard fit and sodium chloride aerosol filtration efficiency testing. This approached can easily adapted to provide point-of-care N95 mask decontamination allowing for increased practical utility of mask recycling in the health care setting.

Influence of Nanoneedles Located on Fibers and Particles on Aerosol Filtration Efficiency

The deposition of aerosol particles in a filter composed of fibers coated with highly porous layers of radially oriented needles and the deposition of needle-coated particles onto smooth fibers have been studied. The Stokes flow fields in a model row of parallel fibers and near an individual needle-coated spherical particle have been calculated. A correction to the Stokes force for the drag of the layer of needles covering the particle has been found. The forces of the van der Waals interaction of the needles with the particle and the fiber have been calculated within the framework of the additive approximation, and the conditions have been determined under which the needles hinder particle deposition onto the fibers.

Aerosol Filtration Testing of Fabrics for Development of Reusable Face Masks

The ongoing outbreak of coronavirus disease of 2019 (COVID-19), triggered by the rapid community spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has brought forward the need for speedy testing and manufacturing of respiratory face masks for global use. Overwhelmed by the fast-growing demand for disposable face masks, many governments have recommended the use of, and elaborated design criteria for, reusable face masks that are meant to slow down the transmission of SARS-CoV-2 in the general population. Using aerosol particle size spectrometers, we performed particle size distribution measurements and calculated the fractional aerosol particle size-selective filtration efficiencies of over 300 fabrics and fabric-assemblies, including chiffon, cotton, synthetics, and various promising layered combinations. We suggest, and experimentally verify, a simple way for estimating the aerosol filtration efficiency of layered fabrics. The analysis herein investigates the relationship between the breathability and filtration properties of fabrics, assemblies of fabrics, and commercial reusable masks from various regions around the globe. In addition, we demonstrate how a hydrophobic coating can provide a statistically significant increase in the fabrics’ filtration efficiency. The insights of this work are crucial to developing non-woven, high-filtration-performance, reusable face masks that can be worn for extended periods of time. © The Author(s).

Copper@ZIF-8 Core-Shell Nanowires for Reusable Antimicrobial Face Masks.

SARS‐CoV‐2 and other respiratory viruses spread via aerosols generated by infected people. Face masks can limit transmission. However, widespread use of disposable masks consumes tremendous resources and generates waste. Here, a novel material for treating blown polypropylene filtration media used in medical‐grade masks to impart antimicrobial activity is reported. To produce thin copper@ZIF‐8 core‐shell nanowires (Cu@ZIF‐8 NWs), Cu NWs are stabilized using a pluronic F‐127 block copolymer, followed by growth of ZIF‐8 to obtain uniform core‐shell structures. The Cu@ZIF‐8 NWs are applied to filtration media by dip coating. Aerosol filtration efficiency decreases upon exposure to ethanol (solvent for dip‐coating), but increases with addition of Cu@ZIF‐8 NWs. Cu@ZIF‐8 NWs shows enhanced antibacterial activity, compared to Cu NWs or ZIF‐8 alone, against Streptococcus mutans and Escherichia coli. Antiviral activity against SARS‐CoV‐2 is assayed using virus‐infected Vero E6 cells, demonstrating 55% inhibition of virus replication after 48 h by 1 µg of Cu@ZIF‐8 NWs per well. Cu@ZIF‐8 NWs’ cytotoxicity is tested against four cell lines, and their effect on inflammatory response in A549 cells is examined, demonstrating good biocompatibility. This low‐cost, scalable synthesis and straightforward deposition of Cu@ZIF‐8 NWs onto filter media has great potential to reduce disease transmission, resource consumption, and environmental impact of waste.

Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks

As a consequence of the COVID-19 pandemic caused by the SARS-CoV-2 virus, the widespread daily use of face masks is promoted worldwide. Particle-size dependent filtration efficiencies (FE; dp = 30 ...

Improvising the surgical helmet system for aerosol-generating procedures in the OR: Surgeon designed 3D printed mould for augmented filtration system

1. BackgroundThe aim of this paper is to describe the process of designing and developing a mould for filter placement via 3D printing on top of the surgical helmet. This mould was designed to affix a filter material on top of the helmet system for use during the COVID - 19 pandemic. 2. MethodThe authors performed 3D scanning of the Stryker Surgical helmet (Stryker T5, REF 400–610, US patents 6,973,677:7,753,682) and created a negative template of the top of the helmet. A mould for filter placement was printed and fitted onto the top of the surgical helmet. This construct was tested to evaluate the surgeon’s comfort, aerosol filtration efficiency etc. 3. ResultThe helmet provided adequate comfort, showed no evidence of staining on spill test and the filter passed the industry filtration efficiency standards. 4. ConclusionThe 3D printed mould is an inexpensive, efficient, and comfortable design to augment personal protection ability of the Stryker helmet system. This process can be extrapolated to 3D print templates for other surgical helmets.

Letter to the Editor Regarding Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks

Letter to the Editor Regarding Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks

Correction to Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks.

Correction to Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks.

Substantial Improvement of Oil Aerosol Filtration Performance Using In-Plane Asymmetric Wettability.

Oil aerosol usually causes air pollution, health issues, and corrosion to equipment. The removal of aerosol oil particles from the air is a crucial process in industrial production and daily life. Although fibrous filters have been a widely used material for the separation of oil aerosol from the air, it is still a challenge to separate submicrometer aerosol oil particles with both high filtration efficiency and low resistance. Herein, we report a novel approach to markedly reduce the pressure drop of a fibrous filter and simultaneously increase its aerosol filtration efficiency, only by surface treatment to make the filter have in-plane alternating superoleophilic and superoleophobic patterns. We used a spraying method to prepare superoleophobic and superoleophilic patterns on the filter. The best filtration results were achieved when two layers of the patterned filters that have superoleophobic and superoleophilic strips (both width, 5 mm) were stacked in a way that the opposite wetting surfaces contacted each other between the layers. The filter showed a much-reduced filtration resistance and the pressure drop (4.16 kPa) at the pseudo-steady state being at least 45% lower when compared to the two-layer controls with a homogeneous surface wettability (i.e., untreated surface, superoleophobicity, and superoleophilicity). It also showed higher filtration efficiency (98.37% for small oil mists and 99.99% for large oil mists) and over two times higher quality factor (0.99 kPa-1 for small oil mists and 2.27 kPa-1 for large oil mists). The asymmetric wettability leads to the formation of unobstructed channels for the air stream to penetrate through the filter matrix, leading to a low resistance with improved oil capture efficiency. The pattern strip width showed an effect on filtration performance. This unexpected finding may provide a novel approach to designing high-performance, low energy consumption, and long-life coalescence filters.

Layer by layer nanocomposite filter for ABC filtration

A multifunctional layer by layer nanocomposite air filter was fabricated by using electrospinning method. Polyacrylonitrile (PAN) nanofibers incorporated with silver nanoparticles (Ag NP) acts as first layer and PAN nanofibers incorporated with magnesium aluminate nanoparticles (MA NP) acts as second layer which was placed between polypropylene spun bonded nonwoven (PP SBN). The morphology of the prepared nanocomposite filter was studied by scanning electron microscopy. The performance of the filter was evaluated against i) bacterial filtration efficiency (BFE) with inhibition property ii) PM2.5 aerosol filtration efficiency (AFE) and iii) chemical detoxification efficiency. The developed nanocomposite air filter showed 99% filtration efficiency against bacterial agent & PM2.5 and 95% detoxification against 2-choloro ethyl ethyl sulfide (2-CEES). The result obtained showed that the developed layer by layer nanocomposite filter has the potential application against ABC removal.

Preliminary Experimental Investigation on the Filtration Performance of Submicron Insoluble Aerosol in a Bubble Column

Pool scrubbing is a representative process for aerosol retention involved in the LWR severe accidents and has proved to be a potential method to removal micron-sized aerosol. Bubble scrubbing as the key component of pool scrubbing, has the advantages of large gas-liquid contact area and long residence time. However, the filtration mechanism of submicron aerosol by bubble scrubbing is still not clear. Therefore, the goal of this research is to evaluate the filtration performance of submicron insoluble aerosol in a bubble column. Some preliminary experiments were carried out to investigate the influence of operation parameter on aerosol filtration efficiency, such as inlet aerosol concentration, gas flow rate and pool temperature. Mass method was used to analyze the aerosol filtration efficiency. The results show that the aerosol filtration efficiency independent of inlet aerosol concentration when inlet aerosol concentration is in the range of 0.2-0.5 g/m3. Besides the aerosol filtration efficiency is influenced by the superfical gas velocity. With the increase of superfical gas velocity, homogeneous bubbling, transition and heterogeneous bubbling regime will appear in turn. The aerosol filtration efficiency decreases in transition regime due to the appearance of large bubble, but increases in heterogeneous bubbling regime account for intense gas-liquid interaction. Moreover, the aerosol filtration efficiency significantly decreases with pool temperature. Because the evaporation rate at the gas-liquid interface will significantly increase as the boiling point is approached, which gives retroaction to aerosol filtration efficiency.

Amphiphobic PFTMS@nano-SiO2/ePTFE Membrane for Oil Aerosol Removal

Synthetic expanded polytetrafluoroethylene (ePTFE) membrane has a wide range of applications, including aerosol and dust removal, and exhibits high dust-removing efficiency, high air permeability, and cost-effectiveness. However, the intrinsic oleophilic surface of ePTFE limits its application in the oil-bearing gas–solid separation process. Herein, we report a surface modification method to prepare amphiphobic ePTFE membranes via coating of a layer of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFTMS) – modified nano-SiO2 onto the surface of ePTFE fibers. The oil contact angle of the modified ePTFE membranes was increased from 0 to 123°, while retaining the initial water contact angle of 142°. The amphiphobic membrane shows excellent oil aerosol filtration efficiency with a comparative low pressure drop and high oil rejection rate of 99.5%. Remarkably, the membrane can be reused after simple rinsing with water. The oil aerosol filtration efficiency of membrane remained as high as 98.5% after five cycles of filtration and cleaning.