The effectiveness of pressurized metered-dose inhalers (pMDIs) relies on correct inhalation technique. While prior studies investigated idealized breathing, the impact of real-life irregularities remains less understood. This study explores how real-life irregularities-pausing, coughing, and premature exhalation-alter aerosol transport and deposition in the airways. Large-eddy simulations combined with a discrete phase model were performed on a realistic male airway geometry extending from the oral cavity to the fourth bronchial generation. Computational predictions were validated against in vitro experiments conducted under constant inhalation. Breathing irregularities substantially modified airflow dynamics and shifted deposition toward the upper airways. Coughing generated the strongest vortical structures and turbulence, followed by premature exhalation. Deposition in the left lung decreased from 19.9% during standard COPD inhalation to 2.1% during exhalation and 0.9% during coughing, while mouth-throat deposition increased to 35.2% during coughing compared to 14.5% under the COPD baseline condition. Exhalation caused higher overall particle loss (27.9%) than coughing (24.1%), but coughing produced more pronounced inertial impaction in the upper airways. Fine particles (< 2µm) were largely exhaled (approximately 80%), whereas particles in the 2-5µm range-considered optimal for deep lung delivery-were redirected and lost under disturbed flow conditions. Irregular breathing patterns markedly decrease deep lung deposition and increase upper airway losses. Repeated puffs without adequate intervals may exacerbate this problem, leading to excessive upper-airway deposition and increasing the likelihood of side effects. These findings provide guidance for physicians to tailor puff number and timing, improving therapeutic efficacy while minimizing risks to patient safety.

ABSTRACT This study develops a gradient composite filtration material for high‐efficiency, low‐resistance PM2.5 protection. The use of a bio‐based gelatin‐carboxymethyl cellulose (CMC) adhesive (6% gelatin+3% CMC) enhanced interlayer bonding while minimizing pore blockage, resulting in a filtration efficiency of 98.6% at a pressure drop of 113.9 Pa. This pressure drop is 20%–30% lower than that achieved with petroleum‐based adhesives, leading to a superior quality factor (QF = 0.037). The gradient structure, which integrates spunbond (S) and meltblown (M) layers, employs synergistic mechanisms—inertial impaction in the outer layer, diffusion capture in the middle layer, and secondary adsorption in the bottom layer—to enhance performance. Experimental results demonstrated exceptional stability under dynamic airflow (10–100 L/min), extreme environmental conditions (temperature: −10°C to 50°C; humidity: 30%–90% RH), and long‐term use (retaining &gt; 95% efficiency over 6 h). The material also showed superior performance and cost‐effectiveness compared to commercial N95 masks, with a material cost of approximately 15 CNY/m 2 . The material also exhibits robust performance under simulated heavy rain, sandstorms, and UV/ozone aging, with filtration efficiency fluctuations below 3.9%. The integration of bio‐adhesive point‐bonding with gradient layering results in a quality factor (QF) 40% higher than that of N95 masks, offering a sustainable alternative for industrial and personal protection.

Coal power plays a crucial role in peak shaving for the power grid, and coal-fired power plants must operate flexibly, and even under ultra-low operational conditions that deviate significantly from the design specifications. Consequently, the flow velocity becomes very low, which may lead to increased ash particles deposition on the heat transfer tubes, severely affecting the performance of coal boiler. The phenomenon of fly ash deposition on the cross-flow heating surfaces of the coal-fired boilers was simulated with the CFD-DEM coupling method in the study, which considers the interactions between particles, particles and tube walls, and consider the influence of fluid flow on particle behavior. The mechanisms and processes governing the deposition of ash particles were examined through the lens of particle dynamics, with a focus on the particle viscosity, flow velocity, and particle size on the ash deposition characteristics. This analysis aims to enhance the understanding of the ash deposition mechanisms. The primary mechanisms of deposition are identified as inertial impaction on the windward side and turbulent diffusion on the leeward side. As the deposition process continues, the scouring action of the fluid, combine with the impact of the high-velocity particles, leads to the disruption of numerous P-P contact forces, resulting in fracture and detachment of the deposited ash layer. In the early stages of deposition, high-viscosity fly ash particles show a maximum deposition efficiency of approximately 24% at a flow velocity of 5 m/s, whereas low-viscosity fly ash particles achieve a maximum deposition efficiency of around 20% at a flow velocity of 3 m/s. The particles deposition is simultaneously influenced by two variables that exert opposing effects: collisional momentum and St number. his indicates that specific velocities and particle sizes will inevitably result in maximum deposition. This work provides some guidance on the ash deposition patterns and fouling behavior of boiler heating surfaces and facilitating more reliable predictions of ash particle deposition and mitigating trends in deposition and fouling.

Abstract Performance evaluation of an air purifier in a controlled chamber environment to assess its effectiveness under varying airflow conditions (within chamber, i.e. recirculation fan (RF) and ceiling fan (CF)) using smoke and salt particles was conducted. Clean Air Delivery Rate (CADR) of an air purifier (AP) was measured following the Association of Home Appliances and Manufacturers (AHAM AC-1:2013) standard, with values of 500 ± 10 m 3 h −1 for smoke, 471 ± 7 m 3 h −1 for ammonium sulphate, and 488 ± 9 m 3 h −1 for potassium chloride particles, closely aligned with the certified (as per GB/T 18801:2015 standard) CADR of 520 m 3 h −1 . These measured values against certified values validated the testing facility and the methodology used for its measurement capabilities. Deposition rate (natural decay) analysis revealed significant size-specific variations, for smoke particles of diameter ≤ 1 and 2 µm, the deposition rates vary from 0.68 to 0.89 h −1 under calm condition (when RF and CF were in off position) to 5.33–7.59 h −1 for turbulent conditions (when RF and CF were on). Ammonium sulphate particles showed a size-dependent (0.5–5 µm) increase in deposition rates, ranging from 0.30 to 3.54 h −1 under calm conditions to 0.84–6.90 h −1 under turbulent conditions. Similarly, potassium chloride particles exhibited deposition rates ranging from 0.48 to 1.72 h −1 under calm conditions, increasing to 0.72–4.14 h −1 under turbulent conditions. Study revealed that size-specific particle removal efficiency of AP varied with particle diameter, effectively removing smaller particles (&lt; 1 µm) under calm conditions due to enhanced Brownian diffusion and effective filtration. While, larger particles exhibited higher removal through inertial impaction and gravitational settling. Under turbulent conditions, increased particle resuspension resulted in lower removal efficiencies across all particle types than calm conditions. These findings emphasize the importance of refining the CADR evaluation standards by incorporating size-specific efficiency metrics and assessing performance under dynamic airflow conditions. Additionally, this study suggests that manufacturers should provide CADR specifications for multiple fan speed settings, enabling for more accurate performance assessments allowing consumers to choose devices that best suit their requirement. Graphical abstract

The upward displacement of molten fuel material (or actinides) from the core region due to a reactor-scale fuel bubble expansion–compression, during energetic core disruptive accident (CDA), is essential in evaluating the accident source term for a pool-type sodium fast reactor (SFR). A numerical model is developed to estimate the molten fuel mass distribution in the reactor vessel at the end of the fuel bubble’s expansion–compression phase. The model evaluates the Lagrangian trajectories of representative fuel droplets during the upward displacement from the damaged core. Subsequently, the fuel mass removed from the core region, the fuel mass absorbed by the sodium pool, and the fuel mass that remains in the bubble region after the cessation of the bubble’s expansion–compression cycles are estimated. The fuel droplet diameters are evaluated by considering both mechanical and thermal modes of fragmentation. The initial fuel bubble temperature ranges from 4200 to 4700 K, and the fuel bubble mass is between 1000 and 3000 kg. These values are typical for a medium-sized pool-type SFR under energetic CDA conditions. The fuel droplet trajectories are evaluated by considering drag and gravity as dominant forces under a dilute flow regime. The local fluid (fuel vapor) velocity required to evaluate droplet trajectories is supplied by a fuel bubble model, which accounts for sodium entrainment and the fuel–sodium heat transfer. Analysis results show that the fuel droplet diameter strongly depends on the initial fuel bubble temperature, and it is insensitive to the fuel bubble mass. Also, the sodium entrainment in the bubble region retards the fuel droplet absorption by the sodium pool. Fuel droplets generated by mechanical fragmentation are effectively removed from the bubble region by gravitational settlement. Similarly, inertial impaction effectively removes the thermal fragmentation–generated fuel droplets from the bubble. Results show that the fuel droplets with diameters less than 3 µm (up to 183 kg) remain suspended in the fuel bubble region at the end of the bubble expansion. These suspended fuel droplets can reach the cover gas space during the subsequent buoyancy rise of the fuel/sodium vapor bubble swarm. Results form the basis for the estimation of the accident source term in a reactor containment building due to the fuel bubble phenomenon under energetic CDA in a pool-type SFR.

Gas sensors based on metal oxide semiconductors dominates part of the gas sensor market due to their relative high sensitivity towards various gas molecules, inexpensive production costs, and miniaturization compatibility [1]. However, to meet the requirements imposed in multiple sectors, many key figure of merits such as selectivity, limit of detection, power consumption, and baseline stability needs to be urgently improved [2]. Manipulating the sensing material at the nanoscale is a common adopted approach to outperform the gas sensing capabilities comparable to their bulk counterparts [3]. In this context, the generation of nanoparticle by spark ablation connected to a programable dry printing system based on inertial impaction aroused as an excellent route to nanomanufacturing gas sensing layers [4]. Spark ablation is a gas-phase nanoparticle (NP) synthesis method that takes place at ambient pressure when pulsed electric discharges are induced between two bulk electrodes. The energy liberated during the discharge locally heat the electrodes [5] ablating the electrode material, leading to the formation of a vapor cloud that is rapidly cool down due to the extinction of the spark and a flowing carrier gas. In this quenching process the vaporized material condensate into atomic clusters that evolve into NPs nucleation that finally forms larger agglomerates (see Figure 1.a). This is a scalable dry gas method to produce NPs with a well-defined size and composition, it is considerable a simple and versatile in view of the multiplicity of materials that can be formed, and environmental friendly since it does not require chemical precursors or binders [5]. The produced NPs can be collected and deposited using inertial impaction, in this case, the aerosol containing the NPs can be accelerated through a nozzle by means of pressure difference between the NP generator reactor and chamber where the target substrate is placed. The production of nanoporous layers (NPLs) or disperse NPs can be controlled depending on the sparking/printing conditions. Herein, ZnO based NPLs were printing on a Si-based platform chip [7] produced with different Ar flows during the spark ablation process. The dry printed NPLs were used as a gas sensing layers towards the detection of a gas mixture of hydrocarbons, named Hcmix (including, acetylene, ethane, ethene, and propene). Figure 1.b shows the NPLs resistance variation upon exposure of the Hcmix. As a result, the NPLs formed using a higher carrier flow leads to a faster response/recovery times but a higher drift baseline was detected. The difference in the gas response are attributed to different porosity and NPs sizes forming the NPLs. Higher carrier flow conducts to a faster quenching process leading to the formation of relative smaller NPs that can affect the agglomerate formation and subsequent NPL deposition. In this work, the impact of the carrier flow on the NPLs formation is discussed and their influence on the gas sensing performance. This works aims to demonstrate the high potential of the nano-printing technology in terms of flexibility for the nanomaterial synthesis to optimize chemical sensors.Figure 1. (a) Schematized of the spark ablation process and the evolution of the NPs formation. (b) Resistance variation upon exposure of Hcmix gas molecules of two NPLs based on ZnO printed by inertial impaction. During the spark ablation process for each NPL, the NPs were generated using different carrier flows (1 l/min and 5 l/min.

Chemical nanosensors based on tin dioxide (SnO2) and zinc oxide (ZnO) nanoparticles (NPs) were developed and characterized for the detection of low concentrations of atmospheric pollutants, such as nitrogen dioxide (NO2) and carbon monoxide (CO). The sensing layers were prepared using three fabrication methods: drop-casting, electrospray, and spark ablation coupled with an inertial impaction printer, to compare their performance. Multiple surface characterization techniques were carried out to investigate the surface morphology and elemental composition of the deposited layers such as SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy) analyses. UV light photoactivation enabled the sensors to detect ultra-low concentrations of the target gases at room temperature (100 ppb NO2 and 1 ppm CO). The measurements were conducted at 50% relative humidity to simulate real environmental conditions. All sensors were capable of detecting the target gases. Drop-casting is the simplest and most cost-effective technique, but it is also the least reproducible. In contrast, sensors based on the spark ablation technique achieved more homogeneous sensing layers, with practically no nanoparticle agglomeration, resulting in devices with lower noise and drift in their electrical response.

Deposition characteristics of ultrafine particles of different shapes in an inertial impactor: CFD-DEM simulations and experiments

Patient-specific simulation of particle dynamics in the respiratory airways from CT-scan-reconstructed images using a continuous phase modelling framework.

Impact of keratin subfractions on the ultrafine particles filtration of sustainable electrospun human hair keratin/PVA nanofibers.

IntroductionAssessment and prediction of health risks caused by exposure to dust particles in ambient air is a relevant task the contemporary healthcare has to tackle. To do it, it is necessary to develop mathematical models that make it possible to estimate introduction of dust particles into the human body.PurposeThe present study focuses on quantification of particles that are deposited in the tracheobronchial (TB) airways (G0–G5) as well as particles able to reach the lungs. We investigate deposition of particles with various sizes and density that are present in ambient air in a large industrial center.MethodsInhaled air is considered a multiphase mixture of a homogenous gas and solid dust particles. We considered non-stationary airflow during light, moderate and vigorous activity.ResultsWe quantified a share of deposited particles (SDP) with various dispersed structure (between 0.5 and 20 µm) and density (1000, 2000, 2700, 4000 kg m–3) in the TB airways; the article provides computed motion paths of particulate matter.Conclusions Particle density mostly influences differences in deposition of micro-sized particles (2.5–20 µm). Deposition of small particles (PM1) slightly depends on particle density and intensity of breathing. Larger particles (2.5–20 µm) are governed primarily by inertial impaction and gravitational settling. As particle sizes and mass go down, SDP in the airways decreases and accordingly there is a growth in the share of particles able to penetrate small airways and reach the lungs. As the micro-sized particles (2.5–20 µm) density increases, the SDP increases, which is typical for all breathing modes. As respiratory intensity increases, SDP grows.Graphical abstract

This paper incorporates various currently known collection mechanisms (including Brownian diffusion, interception effect, inertial impaction, thermophoresis, diffusiophoresis, and electrostatic interaction) into the calculation of the total collection efficiency to analyze their impacts on the scavenging coefficient. The turbulent effect is introduced into the parametric study of the scavenging coefficient. Combining the local raindrop size distribution and aerosol size distribution, a theoretical prediction model for multi-fraction aerosol scavenging by rainfall is established and verified and corrected with measured data. The main conclusions are as follows: For particles within the accumulation mode range, the influence of the collision efficiency needs to be carefully considered. When studying the scavenging coefficient, it is necessary to combine the locally measured raindrop size distribution and aerosol size distribution. The influence of the aerosol size distribution on the scavenging coefficient under different seasonal conditions in the same area can be neglected. When the turbulent effect is introduced, the theoretical prediction is closer to the actual situation. In comparison with the actual measured PM2.5 values in Guangzhou City, Hefei City, and Tianjin City, the temporal variation characteristics of PM2.5 estimated by the theoretical model exhibit a substantial degree of consistency with the trends revealed by the measurement results. Additionally, a linear correlation is discernible between the scavenging coefficients obtained from field measurements in these three regions and those calculated by the theoretical model. Specifically, the equations of the linear relationships are Λs = 0.498 × 10−5 + 1.025Λm; Λs = 1.035Λm − 0.036 × 10−5; and Λs = 0.903Λm − 1.11 × 10−5.

An Eulerian model combined with population balance equation was developed in this study to investigate the coagulation and deposition of polydisperse particles in the human respiratory tract. The mass and moment terms were incorporated into the model to capture the size-dependent particle dynamics such as inertial drift and diffusion deposition. Experiments were conducted using a three-dimensional (3D) printed human upper airway cast under different particle number concentration conditions. The simulation results reached a fair well agreement with the measurement data. The validated model was then applied to analyze the effect of coagulation on a sub micrometer particle size change and deposition fraction. It was predicted that the higher number concentration and longer residence time promoted particle coagulation. A fitting equation for predicting cigarette smoke particle size and number distribution as a function of residence time was provided. Over 90% of particle mass loss in the airway model was attributed to coagulation, with less than 10% due to deposition. The total deposition fraction of cigarette smoke particles was decreased, as the formation of larger particles from coagulation reduced the diffusion effect. However, regional deposition in the larynx was increased due to enhanced inertial impaction. The numerical method provided in this study addressed the limitations of semi-empirical or analytical formulas for deposition prediction, enabling coupled Eulerian simulations of coagulation and deposition in a three-dimensional respiratory tract model. It can also be extended to explore the effects of other aerosol physics that involved size changes, such as particle breakup and growth on the airway deposition within this framework.

This article describes a single-step method for synthesizing nanostructured materials using evaporation-condensation synthesis and inertial impaction of aerosol nanoparticles. The as-deposited films exhibit anisotropic vertical and horizontal sintering of their palladium nanoparticle building blocks, yielding vertical structures. The electrical conductivity of the films is stable and highly sensitive to the presence of hydrogen in the overlaying gas, at concentrations that range from a few hundreds parts per million to a few percent.

Polyelectrolyte multilayer (PEM) membranes, with advantageous features of versatile chemistry and structures, are driving the development of advanced nanofiltration (NF) membranes with exceptional performance. While developing a printing method holds great promise for the eventual mass production of these membranes, reports on the printing method and the underlying mechanisms of membrane formation are currently scarce. Herein, we develop an aerosol-assisted printing (AAP) system for fabricating PEM NF membranes with highly tunable separation characteristics. Our study unveils the three stages of membrane formation from assembly of polyethylenimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS): aerosol deposition, single PE layer formation, and PEM assembly. The droplet deposition is governed by inertial impaction, and the deposited PEs migrate/entangle to form a single PE layer. The thicknesses of the PE layer and PEM exhibit linear growth as the number of printing scan increases. Furthermore, PE interdigitation forms an effective polymeric network barrier, which increases the resistance to solute and water transport. By manipulating the PE deposition mass and layering, PEM membranes with tunable pore radii (0.40-0.56 nm) and water permeability (5-60 L·m-2·h-1·bar-1) were obtained for various water treatment applications, ranging from micropollutant removal to humic acid filtration. Our study offers valuable mechanistic insights into the PEM formation and precise structural adjustment via printing, thus facilitating scalable manufacturing and widespread applications of the PEM NF membranes.

Numerical study on the effect of nozzle-plate distance on the aerosols collection efficiency and deposition on the impaction plate of a multi-nozzle inertial impactor

Accurately locating deposited particles on the impaction plate of an inertial impactor is crucial for mineralogical and geochemical analysis. Since traditional methods relying on filter analysis are costly and time-consuming, this study delves into the numerical examination of the impact of nozzle-converging length (NCL) on the collection efficiency and depositional arrangements of various fine aerosol particles. Three distinct nozzle-converging lengths (NCL = 3, 7, and 13 mm) were simulated and rigorously compared for their performance in particle collection within an eight-nozzle inertial impactor . Comprehensive analysis reveals that varying NCL does not significantly impact the collection efficiency of any investigated particle, with variations within 12% across all sizes in this study. Moreover, while NCL adjustments influence the settling ratio of primary depositions, these effects remain under 35% for all different-sized and shaped particles studied in this article. Furthermore, after examining 120 cases and averaging the collection efficiency for particles of a constant aerodynamic diameter, our findings indicate that the efficiency variations across the three distinct geometries remain under 5%. Consequently, we conclude that the head design of this impactor is independent from NCL. Notably, shorter NCLs result in denser particle accumulation near the nozzle outlet on the impaction plate, with this effect more pronounced for coarser particles. In summary, this research provides valuable insights into the role of nozzle-converging length in aerosol particle collection efficiency and deposition patterns, offering crucial guidance for particle classification and sampling methodologies eliminating the need for filter analysis.

In urban areas, inhalation of fine particles from combustion sources such as diesel engines causes adverse health effects. For toxicity testing, a substantial amount of particulate matter (PM) is needed. Conventional sampling involves collection of PM onto substrates by filtration or inertial impaction. A major drawback to those methodologies is that the extraction process can modify the collected particles and alter their chemical composition. Moreover, prior to toxicity testing, PM samples need to be resuspended, which can alter the PM sample even further. Lastly, the choice of the resuspension medium may also impact the detected toxicological responses. In this study, we compared the toxicity profile of PM obtained from two alternative sampling systems, using in vitro toxicity assays. One system makes use of condensational growth before collection in water in an impinger - BioSampler (CG-BioSampler), and the other, a Dekati® Gravimetric Impactor (DGI), is based on inertial impaction. In addition, various methods for resuspension of DGI collected PM were compared. Tested endpoints included cytotoxicity, formation of cellular reactive oxygen species, and genotoxicity. The alternative collection and suspension methods affected different toxicological endpoints. The water/dimethyl sulfoxide mixture and cell culture medium resuspended particles, along with the CG-BioSampler sample, produced the strongest responses. The water resuspended sample from the DGI appeared least toxic. CG-BioSampler collected PM caused a clear increased response in apoptotic cell death. We conclude that the CG-BioSampler PM sampler is a promising alternative to inertial impaction sampling.

Characterization of size-resolved charge distributions for triboelectrically charged microparticles via electrical mobility analysis coupled to optical particle spectrometry

Analysis of fouling in domestic boilers fueled with non-woody biomass