Aerosol Droplets Research Articles

Performance Characterisation of the Airvo2TM Nebuliser Adapter in Combination with the Aerogen SoloTM Vibrating Mesh Nebuliser for in Line Aerosol Therapy during High Flow Nasal Oxygen Therapy.

High flow oxygen (HFO) therapy is a well-established treatment in respiratory disease. Concurrent aerosol delivery can greatly expediate their recovery. The aim of this work was to complete a comprehensive characterisation of one such HFO therapy system, the Airvo2TM, used in combination with the Aerogen SoloTM vibrating mesh nebuliser. Representative adult, infant, and paediatric head models were connected to a breathing simulator via a collection filter placed at the level of the trachea. A tracheostomy interface and nasal cannulas were used to deliver the aerosol. Cannula size and gas flow rate were varied across the full operating range recommended by the manufacturer. The tracheal and emitted doses were quantified via UV-spectrophotometry. The aerosol droplet diameter at the exit of the nares and tracheal interface was measured via cascade impaction. High gas flow rates resulted in low emitted and tracheal doses (%). Nasal cannula size had no significant effect on the tracheal dose (%) available in infant and paediatric models. Higher gas flow rates resulted in smaller aerosol droplets at the exit of the nares and tracheostomy interface. Gas flow rate was found to be the primary parameter affecting aerosol delivery. Thus, gas flow rates should be kept low and where possible, delivered using larger nasal cannulas to maximise aerosol delivery.

Opposite effects of aerosols and meteorological parameters on warm clouds in two contrasting regions over eastern China

Abstract. The sensitivity (S) of cloud parameters to the influence of different aerosol and meteorological parameters has in most previous aerosol–cloud interaction (aci) studies been addressed using traditional statistical methods. In the current study, relationships between cloud droplet effective radius (CER) and aerosol optical depth (AOD, used as a proxy for cloud condensation nuclei, CCN), i.e., the sensitivity (S) of CER to AOD, are investigated with different constraints of AOD and cloud liquid water path (LWP). In addition to traditional statistical methods, the geographical detector method (GDM) is applied in this study to quantify the relative importance of the effects of aerosol and meteorological parameters, as well as their interaction, on S. Moderate Resolution Imaging Spectroradiometer (MODIS) C6 L3 data and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-5 reanalysis data, for the period from 2008 to 2022, were used to investigate aci over eastern China. Two contrasting areas were selected: the heavily polluted Yangtze River Delta (YRD) and a relatively clean area over the East China Sea (ECS). Linear regression analysis shows that CER decreases with the increase in AOD (negative S) in the moderately polluted atmosphere (0.1<AOD<0.3) over the ECS, whereas, in contrast, CER increases with increasing AOD (positive S) in the polluted atmosphere (AOD>0.3) over the YRD. Evaluation of S as function of the LWP shows that in the moderately polluted atmosphere over the ECS, S is negative in the LWP interval [40 g m−2, 200 g m−2], and the sensitivity of CER to AOD is substantially stronger as LWP is larger. In contrast, in the polluted atmosphere over the YRD, S is positive in the LWP interval [0 g m−2, 120 g m−2] and does not change notably as function of LWP in this interval. The study further shows that over the ECS, the CER is larger for higher low tropospheric stability (LTS) and relative humidity (RH) but lower for higher pressure vertical velocity (PVV). Over the YRD, there is no significant influence of LTS on the relationship between CER and AOD. The GDM has been used as an independent method to analyze the sensitivity of cloud parameters to AOD and meteorological parameters (RH, LTS and PVV). The GDM has also been used to analyze the effects of interactions between two parameters and thus obtain information on confounding meteorological effects on the aci. Over the ECS, cloud parameters are sensitive to almost all parameters considered except for cloud top pressure (CTP), and the sensitivity to AOD is larger than that to any of the meteorological factors. Among the meteorological factors, the cloud parameters are most sensitive to PVV and least sensitive to RH. Over the YRD, the explanatory power of the sensitivity of cloud parameters to AOD and meteorological parameters is much smaller than over the ECS, except for RH, which has a statistically significant influence on CTP and can explain 74 % of the variation of CTP. The results from the GDM analysis show that cloud parameters are more sensitive to the combination of aerosol and a meteorological parameter than to each parameter alone, but confounding effects due to co-variation of both parameters cannot be excluded.

System for measuring size-based distributions of aerosol droplet volume concentrations using the shadow method and calibration procedure

System for measuring size-based distributions of aerosol droplet volume concentrations using the shadow method and calibration procedure

Study on the Mass transfer and hygroscopic behavior of glucose / ammonium sulfate aerosol droplets

Organic aerosols can form semisolid state, glassy state and high viscous state in the atmosphere, which makes aerosols show nonequilibrium kinetic characteristics following the loss of water due to the extended timescales for diffusive mixing. In this study, aerosol optical tweezers (AOTs) and confocal Raman spectroscopy are utilized to investigate the mass transfer of water and the hygroscopicity of internally mixed glucose/ammonium sulfate aerosol droplets with different organic/inorganic molar ratios (OIRs). The characteristic time ratio between the droplet radius and the RH is calculated to describe the mass transfer of water in the droplets. The results shown that the characteristic time ratio of the mixed glucose/ammonium sulfate aerosol droplets is apparently lower than that of pure glucose droplets. And the characteristic time ratio of the mixed droplets decreases with the increase of ammonium sulfate. The hygroscopicity of mixed glucose/ammonium sulfate aerosol droplets is greatly affected by high viscosity organic matter, and the glassy state of glucose suppresses the crystallization of ammonium sulfate in the system. Compared with the pure ammonium sulfate droplets, the efflorescence relative humidity (ERH) of the mixed glucose/ammonium sulfate droplets is delayed and the deliquescence relative humidity (DRH) is advanced. The ERH of the mixed aerosol droplets with molar ratios of 1:4, 1:3 and 1:2 is 35 ± 2%, 32 ± 2.5% and 30 ± 1.5% RH, respectively. And the DRH of the mixed aerosol droplets is 78 ± 1.5%, 76 ± 2% and 74 ± 2.5% RH, respectively. These results improve the understanding of the physical and chemical properties of super viscous organic/inorganic mixed aerosols, and might have important implications for atmospheric chemistry.

Elucidating the behavior of the SARS-CoV-2 virus surface at vapor–liquid interfaces using molecular dynamics simulation

Aerosols play a major role in the transmission of the SARS-CoV-2 virus. The behavior of the virus within aerosols is therefore of fundamental importance. On the surface of a SARS-CoV-2 virus, there are about 40 spike proteins, which each have a length of about 20 nm. They are glycosylated trimers, which are highly flexible, due to their structure. These spike proteins play a central role in the intrusion of the virus into human host cells and are, therefore, a focus of vaccine development. In this work, we have studied the behavior of spike proteins of the SARS-CoV-2 virus in the presence of a vapor-liquid interface by molecular dynamics (MD) simulations. Systematically, the behavior of the spike protein at different distances to a vapor-liquid interface were studied. The results reveal that the spike protein of the SARS-CoV-2 virus is repelled from the vapor-liquid interface and has a strong affinity to stay inside the bulk liquid phase. Therefore, the spike protein bends when a vapor-liquid interface approaches the top of the protein. This has important consequences for understanding the behavior of the virus during the dry-out of aerosol droplets.

Microfluidics produced ATRA-loaded PLGA NPs reduced tuberculosis burden in alveolar epithelial cells and enabled high delivered dose under simulated human breathing pattern in 3D printed head models

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is second only to COVID-19 as the top infectious disease killer worldwide. Multi-drug resistant TB (MDR-TB) may arise because of poor patient adherence to medications due to lengthy treatment duration and side effects. Delivering novel host directed therapies (HDT), like all trans retinoic acid (ATRA) may help to improve drug regimens and reduce the incidence of MDR-TB. Local delivery of ATRA to the site of infection leads to higher bioavailability and reduced systemic side effects. ATRA is poorly soluble in water and has a short half-life in plasma. Therefore, it requires a formulation step before it can be administered in vivo. ATRA loaded PLGA nanoparticles suitable for nebulization were manufactured and optimized using a scalable nanomanufacturing microfluidics (MF) mixing approach (MF-ATRA-PLGA NPs). MF-ATRA-PLGA NPs demonstrated a dose dependent inhibition of Mtb growth in TB-infected A549 alveolar epithelial cell model while preserving cell viability. The MF-ATRA-PLGA NPs were nebulized with the Aerogen Solo vibrating mesh nebulizer, with aerosol droplet size characterized using laser diffraction and the estimated delivered dose was determined. The volume median diameter (VMD) of the MF-ATRA-PLGA NPs was 3.00 ± 0.18 μm. The inhaled dose delivered in adult and paediatric 3D printed head models under a simulated normal adult and paediatric breathing pattern was found to be 47.05 ± 3 % and 20.15 ± 3.46 % respectively. These aerosol characteristics of MF-ATRA-PLGA NPs supports its suitability for delivery to the lungs via inhalation. The data generated on the efficacy of an inhalable, scalable and regulatory friendly ATRA-PLGA NPs formulation provides a foundation on which further pre-clinical testing can be built. Overall, the results of this project are promising for future research into ATRA loaded NPs formulations as inhaled host directed therapies for TB.

Effects of intermittent aerosol forcing on the stratocumulus-to-cumulus transition

Abstract. We explore the role of intermittent aerosol forcing (e.g., injections associated with marine cloud brightening) in the stratocumulus-to-cumulus transition (SCT). We simulate a 3 d Lagrangian trajectory in the northeast Pacific using a large-eddy simulation model coupled to a bin-emulating, two-moment, bulk microphysics scheme that captures the evolution of aerosol and cloud droplet concentrations. By varying the background aerosol concentration, we consider two baseline systems – pristine and polluted. We perturb the baseline cases with a range of aerosol injection strategies by varying the injection rate, number of injectors, and the timing of the aerosol injection. Our results show that aerosol dispersal is more efficient under pristine conditions due to a transverse circulation created by the gradients in precipitation rates across the plume track. Furthermore, we see that a substantial enhancement in the cloud radiative effect (CRE) is evident in both systems. In the polluted system, the albedo effect (smaller but more numerous droplets causing brighter clouds at constant liquid water) is the dominant contributor in the initial 2 d. The contributions from liquid water path (LWP) and cloud fraction adjustments are important on the third and fourth day, respectively. In the pristine system, cloud fraction adjustments are the dominant contributor to the CRE on all 3 d, followed by the albedo effect. In both these systems, we see that the SCT is delayed due to the injection of aerosol, and the extent of the delay is proportional to the number of particles injected into the marine boundary layer.

A method of spraying based on hydrodynamic and ultrasonic influence on the sprayed liquid

The article is devoted to the development of a sprayer based on the method of simultaneous hydrodynamic and ultrasonic influence on the flow of sprayed liquid. The proposed spraying method makes it possible to increase spraying productivity while reducing the size of aerosol droplets. By establishing optimal conditions, with a nozzle diameter of 0.7 mm, an ultrasonic tool diameter of 8 mm and an excess pressure of the sprayed liquid of 0.7 MPa, the atomizer provides a productivity of 9 ml/s and forms an aerosol with droplet sizes D32 = 40 μm. This is primarily due to the establishment of the optimal operating mode and conditions in the cavitation zone, which make it possible to ensure the highest quantitative concentration of cavitation bubbles.

Impact of acidity and surface-modulated acid dissociation on cloud response to organic aerosol

Abstract. Acid dissociation of the organic aerosol fraction has the potential to impact cloud-activating properties by altering aqueous-phase H+ concentrations and water activity but is currently overlooked in most atmospheric aerosol models. We implemented a simple representation of organic acid dissociation in the aerosol–chemistry–climate box model ECHAM6.3–HAM2.3 and investigated the impact on aerosol-forming aqueous sulfur chemistry, cloud droplet number concentrations, and the shortwave radiative effect. Many atmospheric organic acids are also surface-active and may be strongly adsorbed at the surface of small aqueous droplets. The degree of dissociation has recently been observed for several atmospheric surface-active organics with Brönsted acid character to be significantly shifted in the surface, compared to the bulk aqueous solution. In addition to the well-known bulk acidity, we therefore introduced an empirical account of this surface-modulated dissociation to further explore the potential impact on aerosol climate effects. Malonic acid and decanoic acid were used as proxies for atmospheric organic aerosols of different surface-active and acid strengths. Both acids were found to yield sufficient hydrogen ion concentrations from dissociation in an aqueous droplet population to strongly influence aqueous aerosol sulfur chemistry, leading to enhanced cloud droplet number concentrations and a cooling shortwave radiative effect. Further considering the surface modulation of organic acid dissociation, the impact on cloud microphysics was smaller than according to the well-known bulk solution acidity but still significant. Our results show that organic aerosol acid dissociation can significantly influence predictions of aerosol and cloud droplet formation and aerosol–cloud–climate effects and that, even for a well-known bulk solution phenomenon such as acidity, it may be important to also consider the specific influence of surface effects when surface-active acids comprise a significant fraction of the total organic aerosol mass.

Numerical Simulation of Pyrethrin Aerosol Deposition

Highlights A steady state, laminar CFD model was developed to simulate the airflow inside an aerosol exposure chamber. The CFD model predicted the droplet tracks and deposition of various sizes of aerosol droplets. Larger aerosol droplets had higher deposition efficiency. A Higher flow rate, but still within the laminar flow regime, caused lower deposition efficiency for all droplet sizes. Abstract. Aerosol insecticides (e.g., pyrethrin) are widely used for the control of stored products insects inside food facilities. To optimize pyrethrin aerosol application, computational fluid dynamics (CFD) was used to predict airflow and aerosol transport inside a vertical flow aerosol exposure chamber operated under laminar flow conditions. A discrete phase model in ANSYS FLUENT 2021 R1 was developed, and simulations were conducted to track pyrethrin droplets of various diameters (0.1 to 20 µm) and determine their deposition onto Petri dishes located near the center of the chamber. The deposition efficiency of the different aerosol droplet sizes and the effect of two flow rates (5 × 10-4 m3 s-1 and 4 × 10-4 m3 s-1) on deposition efficiency were determined. The results showed that the predicted deposition of pyrethrin aerosol increased with increasing droplet size, largely due to inertial and gravitational effects. Deposition efficiencies decreased with the higher flow rate—with 0.1% to 96.6% predicted deposition efficiencies for the low flow rate and 0.1% to 93.8% for the high flow rate. Results of this study can be used to improve aerosol application methods for stored product insect control. Keywords: Aerosol deposition, Aerosol insecticide, Computational fluid dynamics, Confused flour beetle, Deposition efficiency, Discrete phase model, Numerical simulation, Particle tracking, Pyrethrins, Stored product insect.

Rotating Dielectric Barrier Discharge Plasma Source for Effective Bacterial Decontamination of Bioaerosols

The airborne transmission of pathogens such as bacteria and viruses via aerosols is one of the most insidious ways of spreading diseases, such as COVID-19, hospital-acquired infections (HAIs), and, in the food industry, contamination of processed foods with food pathogens. Due to their small size, the nuclei of such aerosol droplets can remain suspended in the air for a long time and travel long distances. It is thus of high importance to identify increasingly effective solutions in terms of microbial decontamination of air to be used as a stand-alone application or in synergy with traditional techniques (e.g., filters and UV lamps). In this study, a DBD architecture, rotating dielectric barrier discharge, (RDBD) was devised. Its efficacy as a plasma source was tested inside a chamber containing bioaerosols contaminated with <i>Staphylococcus epidermidis</i>. The results showed that RDBD achieves bacterial inactivation levels greater than 3.6 Log 10 CFU, comparable to those achieved with a commercial device operating at comparable ozone concentrations. Moreover, an observable distinction lies in the reduced average discharge power exhibited by RDBD compared to the power output of the commercial device. Additionally, it is noteworthy that the air flow rate elaborated by RDBD surpasses that of the commercial device by a factor of 3.5. Furthermore, the empirical demonstration established a strong correlation between mean discharge power and resulting ozone concentration, underscoring their pivotal roles in bacterial inactivation. Conversely, the voltage range examined in this investigation does not manifest any discernible effect on the inactivation of microorganisms, given comparable power levels and ozone concentrations. Consequently, these last parameters are critical in scaling a plasma source for air decontamination.

Сферические субмикронные порошки с нано-поликристаллической субструктурой — перспективное сырье для получения мелкозернистой высокоплотной керамики (обзор)

The review reflects the unique properties and possible areas of application of submicron non-agglomerating powders from refractory oxides obtained by aerosol-spray pyrolysis. An analysis of the experimental results obtained by researchers at different times convincingly proves the promise of using aerosol nanostructured submicron spherical powders to obtain ceramic materials with a high-density, uniform fine-grained structure without pores. The uniqueness of aerosol powders is due to the presence in the particles of the nano-polycrystalline substructure of a developed network of inter-grain boundaries, which during sintering has a significant impact on the efficiency of diffusion mass transfer and contributes to an increase in the speed and completeness of pores overgrowth. Aerosol powders acquire these properties through the use of ultrasonic spray pyrolysis, where equilibrium physicochemical processes occur in ultra-small local volumes of aerosol droplets, ensuring a high degree of uniformity of the resulting powder. The formed ultrathin substructure of aerosol powders ensures their full sintering at low temperatures, making it possible to obtain high-density ceramic materials with extreme physical and mechanical characteristics. The practical use of nanostructured aerosol powders does not require the use of preliminary preparation operations (grinding-grinding, classification, purification from impurities, etc.) and, unlike ultrafine powders, they are easily molded using traditional methods of powder technology (uniaxial pressing, hot casting, etc.).

Phase transitions of fluorotelomer alcohols at the water|alkane interface studied via molecular dynamics simulation.

Fluorosurfactants are long-lasting environmental pollutants that accumulate at interfaces ranging from aerosol droplet surfaces to cell membranes. Modeling of adsorption-based removal technologies for fluorosurfactants requires accurate simulation methods which can predict their adsorption isotherm and monolayer structure. Fluorotelomer alcohols with one or two methylene groups adjacent to the alcohol (7 : 1 FTOH and 6 : 2 FTOH, respectively) are investigated using the OPLS-AA force field at the water|hexane interface, varying the interfacial area per surfactant. The acquired interfacial pressure isotherms and monolayer phase behavior are compared with previous experimental results. The results are consistent with the experimental data inasmuch as, at realistic adsorption densities, only 7 : 1 FTOH shows a phase transition between liquid-expanded (LE) and 2D crystalline phases. Structures of the LE and crystalline phases are in good agreement with the sticky disc and Langmuir defective crystal models, respectively, used previously to interpret experimental data. Interfacial pressure of the LE phase agrees well with experiment, and sticky disc interaction parameters indicate no 2D LE-gas transition is present for either molecule. Conformation analysis reveals 7 : 1 FTOH favors conformers where the OH dipole is perpendicular to the molecular backbone, such that the crystalline phase is stabilized when these dipoles align.

Oscillating high aspect ratio micro-channels can effectively atomize liquids into uniform aerosol droplets and dial their size on-demand.

Ultrasonic atomization of liquids into micrometer-diameter droplets is crucial across multiple fields, ranging from drug delivery, to spectrometry and printing. Controlling the size and uniformity of the generated droplets on-demand is crucial in all these applications. However, existing systems lack the required precision to tune the droplet properties, and the underlying droplet formation mechanism under high-frequency ultrasonic actuation remains poorly understood due to experimental constraints. Here, we present an atomization platform, which overcomes these current limitations. Our device utilizes oscillating high aspect ratio micro-channels to extract liquids from various inlets (ranging from sessile droplets to large beakers), bound them in a precisely defined narrow region, and, controllably atomize them on-demand. The droplet size can be precisely dialled from 3.6 μm to 6.8 μm by simply tuning the actuation parameters. Since the approach does not need nozzles, meshes or impacting jets, stresses exerted on the liquid samples are reduced, hence it is gentler on delicate samples. The precision offered by the technique allows us for the first time to experimentally visualise the oscillating fluid interface at the onset of atomization at MHz frequencies, and demonstrate its applications for targeted respiratory drug delivery.

Surfaces of Atmospheric Droplet Models Probed with Synchrotron XPS on a Liquid Microjet.

ConspectusThe atmosphere is a key part of the earth system comprising myriad chemical species in all basic forms of matter. Ubiquitous nano- and microscopic aerosol particles and cloud droplets suspended in the air play crucial roles in earth's climate and the formation of air pollution. Surfaces are a prominent part of aerosols and droplets, due to the high surface area to bulk volume ratios, but very little is known about their specific properties. Many atmospheric compounds are surface-active, leading to enhanced surface concentrations in aqueous solutions. Their distribution between the surface and bulk may determine heterogeneous chemistry and many other properties of aerosol and cloud droplets, but has not been directly observed.We used X-ray photoelectron spectroscopy (XPS) to obtain direct molecular-level information on the surface composition and structure of aqueous solutions of surface-active organics as model systems for atmospheric aerosol and cloud droplets. XPS is a vacuum-based technique enabled for volatile aqueous organic samples by the application of a high-speed liquid microjet. In combination with brilliant synchrotron X-rays, the chemical specificity of XPS allows distinction between elements in different chemical states and positions within molecular structures. We used core-level C 1s and N 1s signals to identify the alkyl and hydrophilic groups of atmospheric carboxylic acids, alkyl-amines, and their conjugate acids and bases. From this, we infer changes in the orientation of surface-adsorbed species and quantify their relative abundances in the surface. XPS-derived surface enrichments of the organics follow trends expected from their surface activities and we observed a preferential orientation at the surface with the hydrophobic alkyl chains pointing increasingly outward from the solution at higher concentrations. This provides a first direct experimental observation of well-established concepts of surface adsorption and confirms the soundness of the method.We mapped relative abundances of conjugate acid-base pairs in the aqueous solution surfaces from the respective intensities of distinctive XPS signals. For each pair, the protonation equilibrium was significantly shifted toward the neutral form in the surface, compared to the bulk solution, across the full pH range. This represents an apparent shift of the pKa in the surface, which may be toward either higher or lower pH, depending on whether the acid or base form of the pair is the neutral species. The surface shifts are broadly consistent with the relative differences in surface enrichment of the individual acid and base conjugates in binary aqueous solutions, with additional contributions from nonideal interactions in the surface. In aqueous mixtures of surface-active carboxylate anions with ammonium salts at near-neutral pH, we found that the conjugate carboxylic acids were further strongly enhanced. This occurs as the coadsorption of weakly basic carboxylate anions and weakly acidic ammonium cations forms ion-pair surface layers with strongly enhanced local abundances, increasing the probability of net proton transfer according to Le Chatelier's principle. The effect is stronger when the evaporation of ammonia from the surface further contributes to irreversibly perturb the protonation equilibrium, leaving a surplus of carboxylic acid. These surface-specific effects may profoundly influence atmospheric chemistry mediated by aqueous aerosols and cloud droplets but are currently not taken into account in atmospheric models.

Value of Imprint Cytology for the Rapid Diagnosis of Mucormycosis in the COVID-19 Pandemic Setting - A Pilot Study.

The second wave of the coronavirus disease 2019 (COVID-19) pandemic recorded a surge in rhino-orbital-cerebral mucormycosis (ROCM) infection in COVID-19-positive patients with diabetes and on concomitant steroid therapy. The rapidly progressive and devastating nature of the disease necessitated prompt diagnosis and early intervention to improve patient outcomes. Histopathology and fungal culture remain essential tools; however, these investigations have long and variable turn-around times (TATs) and may delay the initiation of treatment. Frozen section is not widely available and should be avoided in COVID-19-positive cases due to the risk of aerosol production and droplet exposure. In cases with high clinicoradiologic suspicion for mucormycosis, imprint cytologic evaluation provides a rapid diagnosis. Familiarity with fungal cytomorphology, awareness of morphologic pitfalls, and implementation of a standardized reporting format aid in diagnostic accuracy. Eighteen COVID-19-positive patients, who were admitted to our hospital with clinical suspicion of mucormycosis during June and July 2021, were included in the study. We used nasal or oral imprint cytology for the initial, rapid detection of Mucor. Cytology findings were correlated with histopathology and fungal culture results. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. The sensitivity, specificity, PPV, and NPV were 100%, 100%, 100% and 100%, respectively. This study showed that imprint cytology can be a rapid, cost-effective, first-line diagnostic modality in Mucor diagnosis.

Применение ультразвука в процессе аддитивного производства пластиковых деталей

Despite huge prospects for the layer-by-layer synthesis of products, which makes it possible to produce parts of a unique shape, the widespread use of the method face the problems of making a proper microgeometry of the product surface, which due to the peculiarities of layer-by-layer production is rather rough, and mechanical methods of machine working often do not admit the possibility of figure-shaped parts post processing. The article studies the problem of ensuring the quality of the plastic parts surface layer obtained by additive technologies. For this purpose, it is proposed to use ultrasonic processing technologies. The existing methods of using ultrasonic vibrations in the production of plastic parts are analyzed: the manufacture of wire for 3D printing with additives, which results in an increase in the mechanical properties of the product. Besides, liquid treatment of a solvent-loaded product in order to remove supporting elements. Studies have been carried out on the finishing of parts in a solvent aerosol obtained by ultrasonic spraying. This method has a number of advantages in comparison with the treatment in solvent vapors obtained during its heating, which include the possibility of regulating the size of droplets, their moving speed, aerosol concentration, caused by changing the modes of ultrasonic treatment. As a result of experimental studies, it is found that the use of this treatment method eventuates an increase in the quality of the sample surfaces to be worked, and besides, it reduces the height parameters of roughness in the direction perpendicular to the layered growth of the product by more than a factor of ten. The mechanism of changing the microgeometry of the surface is as follows: when aerosol droplets contact the surface, part of the material forming the protrusions dissolves and fills valleys, while in the liquid state; after finishing the work, the material polymerizes, generating a surface with improved features.

Plasmon-enhanced optoacoustic transducer with Ecoflex thin film for broadband ultrasound generation using overdriven pulsed laser diode.

Ultrasonic transducers facilitate noninvasive biomedical imaging and therapeutic applications. Optoacoustic generation using nanoplasmonic structures provides a technical solution for highly efficient broadband ultrasonic transducer. However, bulky and high-cost nanosecond lasers as conventional excitation sources hinder a compact configuration of transducer. Here, we report a plasmon-enhanced optoacoustic transducer (PEAT) for broadband ultrasound generation, featuring an overdriven pulsed laser diode (LD) and an Ecoflex thin film. The PEAT module consists of an LD, a collimating lens, a focusing lens, and an Ecoflex-coated 3D nanoplasmonic substrate (NPS). The LD is overdriven above its nominal current and precisely modulated to achieve nanosecond pulsed beam with high optical peak power. The focused laser beam is injected on the NPS with high-density electromagnetic hotspots, which allows for the efficient plasmonic photothermal effect. The thermal expansion of Ecoflex finally generates broadband ultrasound. The overdriven pulsed LD achieves a maximum optical peak power of 40W, exceeding the average optical power of 3W. The thick Ecoflex-coated NPS exhibits an eightfold optoacoustic enhancement with a fractional bandwidth higher than 160% and a peak frequency of 2.5MHz. In addition, the optoacoustic amplitude is precisely controlled by the optical peak power or the laser pulse width. The PEAT-integrated microfluidic chip clearly demonstrates acoustic atomization by generating aerosol droplets at the air-liquid interface. Plasmon-enhanced optoacoustic generation using PEAT can provide an approach for compact and on-demand biomedical applications, such as ultrasound imaging and lab-on-a-chip technologies.

Effect of the Addition of Diblock Copolymer Nanoparticles on the Evaporation Kinetics and Final Particle Morphology for Drying Aqueous Aerosol Droplets.

A deeper understanding of the key processes that determine the particle morphologies generated during aerosol droplet drying is highly desirable for spray-drying of powdered pharmaceuticals and foods, predicting the properties of atmospheric particles, and monitoring disease transmission. Particle morphologies are affected by the drying kinetics of the evaporating droplets, which are in turn influenced by the composition of the initial droplet as well as the drying conditions. Herein, we use polymerization-induced self-assembly (PISA) to prepare three types of sterically stabilized diblock copolymer nanoparticles comprising the same steric stabilizer block and differing core blocks with z-average diameters ranging from 32 to 238 nm. These well-defined nanoparticles enable a systematic investigation of the effect of the nanoparticle size and composition on the drying kinetics of aqueous aerosol droplets (20-28 μm radius) and the final morphology of the resulting microparticles. A comparative kinetics electrodynamic balance was used to obtain evaporation profiles for 10 examples of nanoparticles at a relative humidity (RH) of 0, 45, or 65%. Nanoparticles comprising the same core block with mean diameters of 32, 79, and 214 nm were used to produce microparticles, which were dried under different RH conditions in a falling droplet column. Scanning electron microscopy was used to examine how the drying kinetics influenced the final microparticle morphology. For dilute droplets, the chemical composition of the nanoparticles had no effect on the evaporation rate. However, employing smaller nanoparticles led to the formation of dried microparticles with a greater degree of buckling.

Effect of size and concentration corrections for surface tension on the hygroscopicity prediction of nano-aerosols

Effect of size and solute concentration on the surface tension of succinic acid (SA)-water aerosol droplets smaller than 10 nm which cannot be obtained experimentally is studied by molecular dynamics (MD) simulations. On this basis, a comprehensive formula for surface tension is proposed and applied to the hygroscopicity model, and predictions are compared with three traditional models. Results show that the surface tension is positively correlated with the droplet size within a certain size range which is shortened with the increasing SA concentration, and the stable surface tension values after a sufficiently large size is validated experimentally. Additionally, the surface tension decreases linearly as the SA concentration increases, and the absolute slope is positively correlated with the size. Moreover, using surface tension formula from this study results in an improvement of the hygroscopicity prediction. The surface tension is found to be the main reason for the difference among various models.