Pore Shape Changes Research Articles

Comparative Pore Structure and Dynamics for Bacterial Microcompartment Shell Protein Assemblies in Sheets or Shells.

Bacterial microcompartments (BMCs) are protein-bound organelles found in some bacteria that encapsulate enzymes for enhanced catalytic activity. These compartments spatially sequester enzymes within semipermeable shell proteins, analogous to many membrane-bound organelles. The shell proteins assemble into multimeric tiles; hexamers, trimers, and pentamers, and these tiles self-assemble into larger assemblies with icosahedral symmetry. While icosahedral shells are the predominant form in vivo, the tiles can also form nanoscale cylinders or sheets. The individual multimeric tiles feature central pores that are key to regulating transport across the protein shell. Our primary interest is to quantify pore shape changes in response to alternative component morphologies at the nanoscale. We used molecular modeling tools to develop atomically detailed models for both planar sheets of tiles and curved structures representative of the complete shells found in vivo. Subsequently, these models were animated using classical molecular dynamics simulations. From the resulting trajectories, we analyzed the overall structural stability, water accessibility to individual residues, water residence time, and pore geometry for the hexameric and trimeric protein tiles from the Haliangium ochraceum model BMC shell. These exhaustive analyses suggest no substantial variation in pore structure or solvent accessibility between the flat and curved shell geometries. We additionally compare our analysis to hydroxyl radical footprinting data to serve as a check against our simulation results, highlighting specific residues where water molecules are bound for a long time. Although with little variation in morphology or water interaction, we propose that the planar and capsular morphology can be used interchangeably when studying permeability through BMC pores.

Multiscale analysis of pore structure in clay due to freeze-thaw

The variation of pore structure due to freeze-thaw (F-T) plays a vital role in revealing the thaw settlement mechanism of soils. In this study, remolded saturated clay specimens experienced unidirectional freezing and natural thawing in an open or closed system (i.e., with or without water supply). X-ray computed tomography (CT) and mercury intrusion porosimetry (MIP) were conducted to analyze pore structural characteristics, including macropores, mesopores, and micropores, along the temperature gradient direction before and after F-T. The longitudinal pore binary images, obtained by processing CT images, were used to assess the changes in porosity, pore shape, and orientation of macropores and mesopores due to F-T. The results indicate that the total longitudinal-sectional porosity and macropore percentage increased, whereas the mesopore percentage decreased. F-T considerably influenced the shape and orientation of macropores but had minimal effects on mesopores. The most significant changes occurred in the unfrozen zone due to F-T in an open system but near the final freezing front in a closed system. Additionally, Micropore porosity, diameter, and thermal fractal dimension were analyzed based on MIP data. The results showed that micropore porosity and diameter decreased, with significant changes occurring in the unfrozen zone of the open and closed systems. The micropore porosity and diameter decreased more in the unfrozen zone and near the final freezing front after F-T in a closed system, whereas a smaller decrease occurred in the frozen zone. The thermal fractal dimension value increases after F-T, indicating that the micropore structure became complex. In general, the multiscale pore analysis demonstrated that pore structure, including macropores, mesopores, and micropores, is significantly affected by F-T in the open system compared to the closed system.

Influences of surface topography of porous titanium scaffolds manufactured by powder bed fusion on osteogenesis

Powder bed fusion (PBF) has emerged as a useful metal-three-dimensional (3D) printing technology for manufacturing porous structures; it has been widely employed for the production of medical implants. Multiple previous reports have suggested that the bone ingrowth characteristics of porous structures, among the most important factors for medical implants, are affected by 3D printing parameters (e.g., pore shape). The topography of 3D-printed metal surfaces can also influence cellular responses, including osteoblast differentiation. The surface topography may change according to the shape of the printed pores. Nevertheless, it remains unclear how the surface topography changes. In addition, it is still unknown how the pore shape and the resulting surface topography can further impact the bone ingrowth efficiency of the porous structure. Therefore, to better understand the relationship, we prepared Ti–6Al–4V specimens with different pore shapes (i.e., circular, triangular, and rectangular) using the PBF method, then analyzed the surface topographies of these 3D scaffolds based on curvature and roughness profiles. Through subsequent in vitro studies, we investigated how changes in pore shape and surface topography affect the activity of Saos-2 human osteosarcoma cells. The results of this study confirmed that the curvature radii and local surface roughness change according to pore shape because of the characteristics of PBF. Furthermore, differences in local surface topography and pore shape led to differences in cell proliferation and differentiation. Through our findings, we anticipate that the meticulous design of pore shape and sophisticated control of the processing parameters, such as laser speed and paths, in the fabrication of orthopedic and dental implants will result in significantly enhanced bone ingrowth efficiency.

Lattice structures in ‘pore shape-stiffness’ framework: A ‘porosity-moment of inertia’ based interpretation

• A novel ‘Porosity-Moment of inertia’ based interpretation. • Helpful to analyze the effect of change in pore shape on the effective stiffness of considered lattice structures at constant porosity levels. • To minimize stress-shielding in scaffolds: A desirable development from the perspective of design of lattices. Existing mathematical models (scaling laws) that correlate stiffness of lattices with their porosity and shape of pores, only suggest the monotonic decrease of stiffness with increase in porosity levels for the given shape of pore. Such mathematical models are of limited use to analyze the effect of change in shape of the pore(s) on the stiffness of lattice at constant porosity levels. To address the highlighted research gap, this work utilizes the archaic concept of classical mechanics (moment of inertia) to propose a normalized parametric tensor for the unified-quantification of the shape of pore(s) in lattices. Micromechanics based results successfully demonstrate the application of suggested framework to improve the understanding, interpretation, and predictability of effect of change in shape of the pore(s) on the stiffness of lattice structures.

Vacuum-Induced Guest N,N'-Diethylformamide Binding in a Metastable Cd5-Based Metal-Organic Framework.

A three-dimensional (3D) metal-organic framework (MOF) of [Et2NH2]2[Cd5(BTB)4(DEF)2]·4.75DEF (1; H3BTB = benzene-1,3,5-tribenzoic acid and DEF = N,N'-diethylformamide) sustained by symmetrical Z-shaped Cd5 secondary building units (SBUs) with an intrinsically metastable host framework has been prepared and characterized. Upon gentle vacuum (800 Pa) at 50 °C, some encapsulated DEF solvates are released, leading to pore-shape changes and Cd2+ coordination geometry distortion. This is followed by DEF solvate migration to only one end of the SBU with concomitant symmetry breaking. Additional time under vacuum promoted further structural distortion and topology changes as authenticated by single-crystal X-ray diffraction studies. This work was initially inspired by unusual gas adsorption isotherms and points to the potentially complicated, nonspectator role of coordinative solvents such as DEF during MOF activation.

Effects of three-dimensional pore structure on effective thermal conductivities of thermal insulation materials

Pore three-dimensional structure and overlap are the key factors in decreasing effective thermal conductivities of the porous insulation material. However, this coupled effect of pore structure and overlap has not been intensively studied. In this work, many three-dimensional models are built to solve the coupled heat transfer in porous insulation materials. The effects of pore structure and overlap are investigated. The results indicate that the effective contact area between pore gas and solid matrix is a key factor for the thermal insulation performance of porous insulation materials. The effect mechanism of the pore overlap on the thermal insulation is affected by the pore shape. The effect of pore overlap on the heat transfer performance is determined by the overlapping direction. The decrease of pore content is also affected by the pore shape. Overall, the pore overlap reduces the thermal insulation performance of porous insulation materials, regardless of pore shape and content change. Cylindrical (⊥) pore has the largest thermal insulation performance in our cases. A quantitative correlation is built to predict the effective thermal conductivity of the porous insulation material with different pore shapes. This correlation is not only simple but also accurate.

Characteristics of Microstructural Changes of Malan Loess in Yan’an Area during Creep Test

The shortage of land resources on the Loess Plateau has long been a thorny problem. Many high-fill projects are carried out, accompanied by a series of geological hazards, which threaten the ecological environment and personal safety. The creep characteristics of loess are an essential part of loess landslide research. The microstructural changes are closely related to creep behavior. By conducting triaxial creep experiments on Malan loess from the Yan’an area in China, scanning electron microscope (SEM) experiments on loess in different creep stages were carried out. Using qualitative and quantitative analyses of the microstructural characteristics of intact loess and remodeled loess during creep, the microstructural parameters were compared, and finally, the microscopic mechanisms during creep were analyzed. The qualitative analysis of remodeled loess during creep returned significantly higher results than it did for intact loess. During the creep process, among the microstructural parameters of loess change, the change in pore and particle size and shape were the most obvious, while the complexity of other microstructural parameters and orientation changed little. During the creep process of loess, the soil skeleton changed continuously, but the loess microstructure featured different changes at different levels of deviator stress.

Real-time imaging of optic nerve head collagen microstructure and biomechanics using instant polarized light microscopy

Current tools lack the temporal or spatial resolution necessary to image many important aspects of the architecture and dynamics of the optic nerve head (ONH). We evaluated the potential of instant polarized light microscopy (IPOL) to overcome these limitations by leveraging the ability to capture collagen fiber orientation and density in a single image. Coronal sections through the ONH of fresh normal sheep eyes were imaged using IPOL while they were stretched using custom uniaxial or biaxial micro-stretch devices. IPOL allows identifying ONH collagen architectural details, such as fiber interweaving and crimp, and has high temporal resolution, limited only by the frame rate of the camera. Local collagen fiber orientations and deformations were quantified using color analysis and image tracking techniques. We quantified stretch-induced collagen uncrimping of lamina cribrosa (LC) and peripapillary sclera (PPS), and changes in LC pore size (area) and shape (convexity and aspect ratio). The simultaneous high spatial and temporal resolutions of IPOL revealed complex ONH biomechanics: i) stretch-induced local deformation of the PPS was nonlinear and nonaffine. ii) under load the crimped collagen fibers in the PPS and LC straightened, without torsion and with only small rotations. iii) stretch-induced LC pore deformation was anisotropic and heterogeneous among pores. Overall, with stretch the pores were became larger, more convex, and more circular. We have demonstrated that IPOL reveals details of collagen morphology and mechanics under dynamic loading previously out of reach. IPOL can detect stretch-induced collagen uncrimping and other elements of the tissue nonlinear mechanical behavior. IPOL showed changes in pore morphology and collagen architecture that will help improve understanding of how LC tissue responds to load.

Study of the elastic properties of porous copper fabricated via the lost carbonate sintering process

Porous copper has numerous potential applications due to its attractive properties such as high ductility, good corrosion resistance, high surface area, good thermal and electrical conductivity, etc. Within the scope of this work, porous copper samples with 27–67 vol% porosity were fabricated using a mixture of copper powder and potassium carbonate powder, employed as space holders. The sample fabrication process involved the steps of powder mixing, uni-axial pressing, sintering, and final washing. Detailed structural analyses of the fabricated samples were performed by density measurement following Archimedes’ principle, X-ray diffraction for phase analysis, and scanning electron microscopy for microstructural analysis. Three longitudinal elastic constants in each sample were determined in a non-destructive manner using ultrasound phase spectroscopy. Due to the applied uni-axial pressure and the resulting change in pore shape, the fabricated porous copper samples displayed transversely isotropic symmetry. A detailed analysis of the influence of pore shapes and morphologies on the experimentally determined longitudinal elastic constants has been carried out. The results have been compared with the predictions from different micromechanical models for the dependence of elastic constants on porosity.

Pressure and guest-mediated pore shape modification in a small pore MOF to 1200 bar.

Guest-mediated pore-shape modification of the metal-organic framework, Sc2BDC3 upon adsorption of n-pentane and isopentane is examined from 50-1200 bar. Rotation of the BDC linker responsible for the change in pore shape occurs at much lower pressures than previously reported, with distinct adsorption behaviour observed between pentane isomers.

Analysis of Microstructure Evolution and Mechanical Properties during Compression of Open-Cell Ni-Foams with Hollow Struts Using Micro-CT and FEM.

Based on electron backscatter diffraction (EBSD), hollow structures of Ni foam struts fabricated by electroplating on a chemically removable template were observed. Three-dimensional (3D) pore structures of Ni foams were also obtained using X-ray computed tomography (CT), and microstructural features such as porosity, pore size and strut thickness were statistically quantified. Evolution of microstructure and mechanical properties during ex situ compression of open-cell Ni-foams was investigated based on X-ray CT, and experimental results were compared with predictions by the finite element method (FEM). 3D microstructures obtained by X-ray CT revealed that the stress drop started with the buckling of struts at the center of the Ni-foams. The flow stress increased after the buckling of the struts spreads to most of the regions. For effective simulation of the compressive deformation and determination of the microstructural evolution, small domains of interest were selected from the entire set of observed 3D microstructures based on X-ray CT, and struts of Ni foams with a hollow structure were simplified with relevant thin-solid struts. Numerical 3D modeling comprehensively disclosed that compression caused the transverse buckling of the struts, with the bending and buckling of struts thus reducing the stress. Thickness variation of the struts causes a change in the porosity of Ni-foams without a change in pore shape or connectivity. The overall range of strut thickness was from 59 to 133 m, and the range of porosity values was from 80% to 93.7%. A stress drop was predicted with a decrease in the strut thickness or an increase in the porosity, as measured experimentally. It was also found that the stress drop contributed to an increase in the calculated energy absorption efficiency.

Repair of critical-size porcine craniofacial bone defects using a collagen–polycaprolactone composite biomaterial

Regenerative medicine approaches for massive craniomaxillofacial (CMF) bone defects face challenges associated with the scale of missing bone, the need for rapid graft-defect integration, and challenges related to inflammation and infection. Mineralized collagen scaffolds have been shown to promote mesenchymal stem cell osteogenesis due to their porous nature and material properties, but are mechanically weak, limiting surgical practicality. Previously, these scaffolds were combined with 3D-printed polycaprolactone (PCL) mesh to form a scaffold-mesh composite to increase strength and promote bone formation in sub-critical sized porcine ramus defects. Here, we compare the performance of mineralized collagen–PCL composites to the PCL mesh in a critical-sized porcine ramus defect model. While there were no differences in overall healing response between groups, our data demonstrated broadly variable metrics of healing regarding new bone infiltration and fibrous tissue formation. Abscesses were present surrounding some implants and PCL polymer was still present after 9–10 months of implantation. Overall, while there was limited successful healing, with 2 of 22 implants showed substantial levels of bone regeneration, and others demonstrating some form of new bone formation, the results suggest targeted improvements to improve repair of large animal models to more accurately represent CMF bone healing. Notably, strategies to increase osteogenesis throughout the implant, modulate the immune system to support repair, and employ shape-fitting tactics to avoid implant micromotion and resultant fibrosis. Improvements to the mineralized collagen scaffolds involve changes in pore size and shape to increase cell migration and osteogenesis and inclusion or delivery of factors to aid vascular ingrowth and bone regeneration.

Impacts of tillage and nutrient management on soil porosity trends in dryland agriculture

AbstractIn dryland Mediterranean semi‐arid areas, the use of slurries and no‐till are encouraged to reduce costs. This paper evaluates the effect of such practices in terms of morphological changes of the topsoil porosity. The experiment had seven fertilization strategies (five of them including pig slurries applied at cereal sowing or at tillering) combined with no‐till or tillage by disc‐harrowing at sowing. Soil was classified as a Typic Xerofluvent. Texture was silt loam. Pores in the apparent pore diameter (APD) intervals higher than >15 μm and at intervals up to 400 μm were studied with a micromorphological approach plus image analysis. Fifty‐four undisturbed and surface soil samples (0.06 m deep) were analysed. Samples were collected in the third year after the establishment of tillage treatments and throughout the cereal growing season: just before tillage, at cereal tillering and at grain maturity. The incorporation of slurry at pre‐sowing (~2 Mg ha−1 of organic matter ha−1) enhanced porosity (>15 μm) by 33% in the cropping season but mainly in the 200–400‐μm class. Similar behaviour was observed in plots without topdressing fertilization, when till was compared with no‐till. Thus, the potential movement of water and nutrients due to bypass flow was increased. When slurries were only applied at cereal tillering, only the tillage treatment increased topsoil porosity at grain maturity in the 15–100‐μm class by 22% and, thus, increased those pores responsible for soil and water storage. Temporary changes in pore shape after tillage can be explained by microstructure collapse and compaction followed by a partial porosity recovery by faunal activity at grain maturity.Highlights Slurry at pre‐sowing, combined with tillage, increases topsoil coarse pores Tillage increases mesoporosity at grain maturity regardless of the slurry fertilization strategy Pore shape changes after tillage are not further visible at grain maturity No‐till tends to compact silty topsoils, creating platy structures later counteracted by fauna

Evolution of internal pores within AlSi10Mg manufactured by laser powder bed fusion under tension: As-built and heat treated conditions

The optimisation of processing parameters to produce high densification AlSi10Mg parts by laser powder bed fusion (LPBF) has received considerable attention in recent years. Nonetheless, it is important to consider the potential presence of as-built large pores in real world applications, e.g. due to limitations of the available LPBF system, time and cost constraints associated with producing near-perfect density and so on. In this work, recycled powder was used to fabricate AlSi10Mg specimens with sub-optimal densification by LPBF and an experimental investigation into the evolution of specimen porosity occurring under increasing tensile load was performed. A combination of high-resolution X-ray micro computed tomography (XμCT) and an in-situ micro-testing stage was employed to acquire 3D images at different loading stages. Specimens were tested in the as-built condition and following hot isostatic pressing (HIPping) or HIPping with T6. As-built porosity did not change markedly in the lead-up to brittle-like fracture. Pores within ductile HIPped specimens were uniformly elongated up to the onset of damage propagation and pore coalescence. Pore shape change occurred largely without volume change at small extension. HIPping plus T6 produced a compromise between as-built and HIPped conditions in terms of the extent of pore modification observed prior to failure.

Analysis of Thermal-Mechanical Properties of Silicon Dioxide/Polyvinylidene Fluoride Reinforced Non-Woven Fabric (Polypropylene) Composites.

In this paper, solution casting method is used to prepare the PP (polypropylene) non-woven fabric based composite film filled with silicon dioxide/polyvinylidene fluoride (SiO2/PVDF). The mechanical and thermodynamic properties of PP/SiO2/PVDF composites were studied by a uniaxial tensile test under different temperature and combustion experiment. It is found that the stress of PP/SiO2/PVDF composite film with 4 wt % SiO2 is the maximum value, reaching 18.314 MPa, 244.42% higher than that of pure PP non-woven. Meanwhile, the thermal–mechanical coupling tests indicate that with the increase of temperature, the ultimate stress and strain of the composite decrease. At the same time, the thermal shrinkage property of the composite during the heating process is studied. The modified composite has good thermal stability under 180 °C. Scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric (TG) were used to characterize the pore shape, distribution and crystal phase change of the composite. The modified PP/SiO2/PVDF composite film structure shows high strength and good thermal stability, and can better meet the requirements of strength and thermal performance of lithium-ion battery during the charging and discharging process.

Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments

Injection of CO2 into carbonate rocks causes dissolution and alters rock transport properties. The extent of the permeability increases, due to the increased pore volume and connectivity, strongly depends on the regimes of transport and dissolution reactions. Identification of these regimes and their parametrization at the microscopic scale is required for an understanding of the injection processes, and, afterward, for calculating the effective macroscopic parameters for field-scale simulations. Currently, a commonly used approach for calculating the rock effective parameters is the Pore Network Method, PNM, but a better understanding of the validity of its basic assumptions and their areas of applicability is essential. Here, we performed a combined microscopic experimental and numerical study to explore pore-shape evolution over a wide range of transport and dissolution reaction regimes. Experiments were conducted by flowing an acidic solution through a microscopic capillary channel in a calcite crystal at two different flow rates. The experimental results were used to validate our pore-scale reactive transport model that could reproduce the measured effluent composition as well as pore shape changes. Two key stages in pore shape evolution were observed, a transient phase and a quasi-steady-state phase. During the first stage, the shape of the single pore evolved very fast, depending on the flow regime. Under advective-dominant flow, the pore shape remained nearly cylindrical, while under diffusive-dominant transport, the pore shape developed into a half-hyperboloid shape. During the quasi-steady-state stage, the pore volume continued to increase, however, without or with diminutive change of the pore shape. In this stage, only a long period of injection may result in a significant deviation of the pore shape from its original cylinder shape, which is a common assumption in PNMs. Furthermore, we quantitatively evaluated the impact of evolved pore shape spectrum on the conductance calculations and compared it to the formulations currently used for pore network modeling of reactive transport. Under low flow rates, neglecting the developed non-uniform pore shape during the non-steady stage may lead to an overestimation of pore conductance up to 80%.

Mechanical and Tribological Properties of Polyethylene Terephthalate Track-Etched Membranes after Steam and Radiation Sterilization

Abstract—The article presents the results of studying the mechanical characteristics and tribological properties of PET track-etched membranes (TM) obtained by irradiating PET films with argon ions and subsequent etching. The article also shows the changes in the TM mechanical and tribological properties after radiation and steam sterilization. It is established that the sterilization process reduces elongation at break, the Young’s modulus, relative yield strength, and tensile stress. Tribological tests of TM demonstrated a friction coefficient of 0.08–0.17. The tests also showed the nature of the counterbody impact on the material surface, manifested in the formation of “grooves” of various sizes, “jamming” of the surface, and change in pore shape. It was established that TM sterilization does not significantly affect the behavior of the friction coefficient or nature of counterbody impact on the membrane surface.

Microstructure Characteristics and Quantitative Analysis of Collapsible Loess in Xining Area

According to the confined compression test in Xining area, the variation law of pressure on the collapsible deformation and compress deformation of loess is analyzed. The qualitative and quantitative analysis of the microstructure of loess samples before and after collapsing is carried out by electron microscopy. The relationship between the microstructure of the loess sample and the collapsible deformation is analyzed. The results show that:(1)with the increase of pressure, the deformation and compression of loess collapsing gradually become smaller, the soil is compacted, the strength is increased, the compressibility is weakened, the collapsibility is weakened or no collapsibility; (2) with the increase of pressure, the microscopic image observation of the sample before immersion, the structure of the undisturbed soil sample is relatively loose, the pores and particles are clearly distinguished, and the particle contour is relatively clear. After the sample is immersed in water, the arrangement of the skeleton particles becomes very tight, and the pore shape changes from large become small. As the pressure continues to increase, the microstructure of the sample gradually becomes dense; (3) the pressure increases with the increase of pressure before and after immersion in water. The arrangement gradually became stable, the particle distribution gradually concentrated and the degree of agglomeration became higher, and the proportion of pore area gradually decreased. The macroscopic collapse deformation and compression deformation of the loess before and after water immersion were consistent.

Supercritical CO2 Exposure-Induced Surface Property, Pore Structure, and Adsorption Capacity Alterations in Various Rank Coals

Carbon dioxide (CO2) has been used to replace coal seam gas for recovery enhancement and carbon sequestration. To better understand the alternations of coal seam in response to CO2 sequestration, the properties of four different coals before and after supercritical CO2 (ScCO2) exposure at 40 °C and 16 MPa were analyzed with Fourier Transform infrared spectroscopy (FTIR), low-pressure nitrogen, and CO2 adsorption methods. Further, high-pressure CO2 adsorption isotherms were performed at 40 °C using a gravimetric method. The results indicate that the density of functional groups and mineral matters on coal surface decreased after ScCO2 exposure, especially for low-rank coal. With ScCO2 exposure, only minimal changes in pore shape were observed for various rank coals. However, the micropore specific surface area (SSA) and pore volume increased while the values for mesopore decreased as determined by low-pressure N2 and CO2 adsorption. The combined effects of surface property and pore structure alterations lead to a higher CO2 adsorption capacity at lower pressures but lower CO2 adsorption capacity at higher pressures. Langmuir model fitting shows a decreasing trend in monolayer capacity after ScCO2 exposure, indicating an elimination of the adsorption sites. The results provide new insights for the long-term safety for the evaluation of CO2-enhanced coal seam gas recovery.

Optical microscopic study of surface morphology and filtering efficiency of face masks.

BackgroundLow-cost face masks made from different cloth materials are very common in developing countries. The cloth masks (CM) are usually double layered with stretchable ear loops. It is common practice to use such masks for months after multiple washing and drying cycles. If a CM is used for long time, the ear loops become stretched. The loop needs to be knotted to make the mask loop fit better on the face. It is not clear how washing and drying and stretching practices change the quality of a CM. The particulate matter (PM) filtering efficiency of a mask depends on multiple parameters, such as pore size, shape, clearance, and pore number density. It is important to understand the effect of these parameters on the filtering efficiency.MethodsWe characterized the surface of twenty different types of CMs using optical image analysis method. The filtering efficiency of selected cloth face masks was measured using the particle counting method. We also studied the effects of washing and drying and stretching on the quality of a mask.ResultsThe pore size of masks ranged from 80 to 500 μm, which was much bigger than particular matter having diameter of 2.5 μm or less (PM2.5) and 10 μm or less (PM10) size. The PM10 filtering efficiency of four of the selected masks ranged from 63% to 84%. The poor filtering efficiency may have arisen from larger and open pores present in the masks. Interestingly, we found that efficiency dropped by 20% after the 4th washing and drying cycle. We observed a change in pore size and shape and a decrease in microfibers within the pores after washing. Stretching of CM surface also altered the pore size and potentially decreased the filtering efficiency. As compared to CMs, the less frequently used surgical/paper masks had complicated networks of fibers and much smaller pores in multiple layers in comparison to CMs, and therefore had better filtering efficiency. This study showed that the filtering efficiency of cloth face masks were relatively lower, and washing and drying practices deteriorated the efficiency. We believe that the findings of this study will be very helpful for increasing public awareness and help governmental agencies to make proper guidelines and policies for use of face mask.