Assisted Atomization Research Articles

Revealing the improved thermoelectric performances of (BiSb)2Te3 alloy through rapid solidification of cold-water assisted water atomization approach

Revealing the improved thermoelectric performances of (BiSb)2Te3 alloy through rapid solidification of cold-water assisted water atomization approach

Direct numerical simulation of a subcritical coaxial injection in fiber regime using sharp interface reconstruction

The numerical simulation of space launchers combustion chambers is a topic of increasing interest, as it may help the development of safer and more efficient designs. Understanding fuel injection is a particularly severe challenge. The liquid oxygen is injected by a round orifice surrounded by an annular gaseous stream of fuel, leading in subcritical conditions to a two-phase assisted atomization process. The result of this process is a very dense and polydisperse two-phase flow, which strongly influences the behavior of the chamber. Experimental investigation of this flow is difficult due to the axisymmetric geometry and the dense characteristic of the spray. Neither RANS nor Large Eddy Simulation (LES) possess reliable models able to reproduce the smallest scales of atomization, one of the reasons being the lack of relevant experimental data. Therefore, this work aims to provide detailed information on the atomization process using Direct Numerical Simulation. This paper presents a Direct Numerical Simulation (DNS) of a coaxial liquid–gas assisted atomization in the typical fiber regime encountered in cryogenic injectors. This study aims to better understand the evolution of liquid topology and extract relevant information that may help develop larger-scale models. The flow was first analyzed in terms of topology statistical data, using a dedicated detection and classification algorithm that could characterize the individual liquid structures. These include the central liquid core, the ligament created during primary atomization, and the spherical droplet obtained at the end of the atomization process. Subsequently, a more global statistical topology indicator was investigated, namely the interface area density distribution. This quantity is used in larger-scale RANS or LES models to predict the smallest scales of atomization. Therefore, understanding its behavior in a realistic case is of utmost importance. The interface area density distribution was correlated to the global jet behavior and the liquid topology data obtained by the detection algorithm. The results showed, in particular, a strong correlation between the initial increase of liquid–gas interface area density with the generation of ligaments and between the continuous decrease of the interface area density during droplet formation and stabilization.

Interface area density model for Large-Eddy Simulation of assisted atomization in fiber regime

In the context of simulating liquid rocket engines (LREs), accurately reproducing the complex combustion chamber environment poses a significant challenge. Recent works have shown that Direct Numerical Simulation has made good progress in achieving the simulation of the whole range of temporal and spatial two-phase flow scales involved. However, due to the computational costs, it is currently out of reach in an industrial context. Large-Eddy Simulations (LES) considerably reduce the computational cost but require modeling the two-phase flow at sub-grid level. A promising approach for such modeling is the interface area density (IAD) approach, which was developed initially for LES of flame fronts and subsequently adapted to Diesel jet atomization to recover spray droplet size distributions. In this method, a subgrid density of interface area is transported with an advection equation, while opportune source terms simulate its growth by breakup or its reduction by coalescence effects. In the context of the LREs assisted atomization, the complex mechanism of the assisted atomization in fiber regime must be taken into account by the subgrid model to recover the correct spray size distribution. The present work proposes a new interface area density evolution modeling for two-phase LES of coaxial assisted atomization in fiber regime. The proposed model focuses on recovering a realistic liquid-gas relative velocity at all the scales, enabling accurate modeling of sub-grid scales by using the IAD as a measure of liquid structure sizes.

Salicylic Acid Co-Precipitation with Alginate via Supercritical Atomization for Cosmetic Applications.

Alginate-based microparticles were produced via supercritical assisted atomization (SAA) with the aim of obtaining a biocompatible and low-cost carrier for the delivery of active compounds in cosmetic applications. Salicylic acid was selected as an active model compound, and it was co-precipitated with alginate via SAA, operating at 82 bar and 80 °C. In particular, the drug-to-polymer weight ratio was fixed at 1/4, whereas polymer concentration was varied from 5 to 20 mg/mL in the starting aqueous solution. Operating in this way, alginate-salicylic acid microparticles were characterized by a mean diameter of 0.72 ± 0.25 µm, and the active compound became amorphous after processing. A salicylic acid encapsulation efficiency close to 100% was reached, and the drug release time from the biopolymeric microparticles was prolonged up to nine times with respect to untreated salicylic acid powder.

Lycopene extract from tomato concentrate and its co-precipitation with PVP using hybrid supercritical processes

In this work, a hybrid supercritical approach was proposed for the production of a dried lycopene extract and its co-precipitation in polyvinylpyrrolidone (PVP) sub-microparticles. In particular, lycopene extract was obtained from a tomato pulp concentrate, using ethyl acetate as the optimal organic solvent. Then, the lycopene extract was dried via supercritical antisolvent extraction, operating at 9.0 MPa and 50 °C. In a single step, a solvent-free powder that preserved up to 80 % of antioxidant activity was obtained. To improve lycopene extract shelf-life, supercritical assisted atomization was performed. The aim was to co-precipitate the active principle with a hydrophilic polymer, like PVP, to protect lycopene from oxidation phenomena. Operating at 8.5 MPa and 80 °C, sub-microparticles of 194 ± 230 nm mean diameter were produced that maintained around 85 % of antioxidant activity at least for 6 months of storage at room temperature.

Immediate Release Formulation of Inhaled Beclomethasone Dipropionate-Hydroxypropyl-Beta-Cyclodextrin Composite Particles Produced Using Supercritical Assisted Atomization.

In this study, the enhanced solubilization performance of a poorly soluble drug, beclomethasone dipropionate (BDP), was investigated using hydroxypropyl-β-cyclodextrin (HP-β-CD) and ethanol. The enhanced solubility of the drug was determined using the phase solubility method and correlated as a function of both HP-β-CD and ethanol concentrations. The effective progress of drug solubility originated from the formation of cyclodextrin and BDP inclusion complexes and increase in the lipophilicity of the medium, by aqueous ethanol, for hydrophobic BDP. BDP and HP-β-CD composite particles were produced using supercritical assisted atomization (SAA) with carbon dioxide as the spraying medium, 54.2% (w/w) aqueous ethanol as the solvent, and an optimal amount of the dispersion enhancer leucine. The effect of the mass ratio of HP-β-CD to BDP (Z) on the in vitro aerosolization and in vitro dissolution performance of BDP–HP-β-CD composite particles was evaluated. The aerosolization performance showed that the fine particles fraction (FPF) of the composite particles increased with increasing mass ratio. The water-soluble excipient (HP-β-CD) effectively enhance the dissolution rate of BDP from composite particles. This study suggests that BDP–HP-β-CD composite particles produced using SAA can be employed in immediate-release drug formulations for pulmonary delivery.

Application of sol-gel assisted ultrasound-induced atomization in the mesostructuring of nickel aluminate UF membranes

The research article presents a feasible approach to fabricate supported nickel aluminate ultrafiltration (UF) membranes. The synthesis involves an environmentally benign aqueous sol-gel method and ultrasound induced atomization technique. The process shows uniform microstructural evolution of temperature induced grain growth that transformed the surface of alumina supports into a porous metal oxide framework with porosity in the UF range. The aqueous permeability of the supported membranes was measured using the Hagen Poiseuille membrane model of the parallel open pores. The maximum value of membrane MWCO and permeability was 17 kDa and 42 LMH bar−1, respectively. The features like permeation characteristics and retention behavior indicate the potential use of supported NiAl2O4 membranes for wastewater treatment as UF membranes.

Monofiber optical probe using Doppler signals detection for Drop Size and Velocity measurement in air assisted atomization

Reliable measurement of droplet/bubble size and velocity distributions in dense flows is desired in a variety of research fields, both for laboratory and industrial use. A new type of single-mode monofiber optical probe manufactured by A2 Photonic Sensors is introduced in this paper: it combines traditional phase detection with the collection of a Doppler signal returned by an incoming gas-liquid interface to provide information on residence times, drop concentration and velocity, which afford then drop chords and liquid flux measurements. Compared with classical optical probes, that new sensor does not require any calibration. The purpose of the present work is to test this technique in assisted atomization in order to provide a mean for spray characterization and ultimately to improve our understanding of atomization mechanisms. The probe has been tested downstream of a coaxial air-assisted atomizer operated at liquid velocity =. to. / , and gas velocity from = to about /. We first analyzed raw signals in various flow conditions. It happens that, when increasing the gas velocity and the number density of drops, the signal experiences very strong fluctuations of the gas level, making the identification of individual droplets more difficult. That leads us to develop a new signal processing routine specifically adapted to such complex working conditions. At = / and for three liquid flow rates, the spatial integration of local liquid fluxes represents 92 to 99% of the injected liquid flow rate. These good results demonstrate that the Doppler probe provides reliable statistics on drops velocity and size.

Characterization and Aerosolization Performance of HydroxyPropyl-Beta-Cyclodextrin Particles Produced Using Supercritical Assisted Atomization.

In this study, hydroxypropyl-beta-cyclodextrin (HP-β-CD) particles were produced using supercritical assisted atomization (SAA) with carbon dioxide as the spraying medium or co-solute and aqueous ethanol solution as the solvent. The effects of several key factors on the morphology and size of the HP-β-CD particles were investigated. These factors included the solvent effect, temperatures of the precipitator and saturator, concentration of the HP-β-CD solution, and flow rate ratio of carbon dioxide to the HP-β-CD solution. The conducive conditions for producing fine spherical particles were 54.2% (w/w) aqueous ethanol as the solvent; precipitator and saturator temperatures of 373.2 K and 353.2 K, respectively; a flow rate ratio of carbon dioxide to HP-β-CD solution of 1.8; and low concentrations of HP-β-CD solution. The addition of leucine (LEU) enhanced the aerosol performance of the HP-β-CD particles, and the fine particle fraction (FPF) of the HP-β-CD particles with the addition of 13.0 mass% LEU was 1.8 times higher than that of the HP-β-CD particles without LEU. This study shows that LEU can act as a dispersion enhancer and that HP-β-CD particles produced using SAA can be used as pulmonary drug carriers.

Formulation of inhalable beclomethasone dipropionate-mannitol composite particles through low-temperature supercritical assisted atomization

Mannitol carrier and drug-carrier composite particles were produced via low-temperature supercritical assisted atomization (LTSAA). The enhanced aerosolization of the mannitol carrier particles with added L-leucine could be attributed to the formation of fine corrugated particles, which reduced the interparticle cohesion and led to better flowability of the mannitol carrier particles. A poorly water-soluble drug, beclomethasone dipropionate (BDP), and mannitol co-precipitated during LTSAA with the optimal addition of 9.1 mass % L-leucine. The in vitro aerosolization and dissolution experiments indicated that the fine particles fraction (FPF) of the drug-carrier composite particles was 3.4 times (FPF = 49.9 %) higher than that of the as-received BDP (FPF = 14.7 %) and the 63.2 % drug release time of the drug-carrier composite particles was 15.6 times faster than that of as-received BDP. This study suggests that the drug-carrier composites produced using LTSAA can be employed in the instant formulation of inhalable dry powder.

Formation of Polyethylene Glycol Particles Using a Low-Temperature Supercritical Assisted Atomization Process.

Polyethylene glycol (PEG) particles were prepared using low-temperature supercritical assisted atomization (LTSAA) with carbon dioxide as the spraying medium or the co-solute and acetone as the solvent. The effects of several key factors on the particle size were investigated. These factors included the concentration of the PEG solution, precipitator temperature, saturator temperature, ratio of the volumetric flow rate of carbon dioxide to the PEG solution, and the molecular weight of PEG. Spherical and non-aggregated PEG particles, with a mean size of 1.7–3.2 µm, were obtained in this study. The optimal conditions to produce fine particles were found to be a low concentration of the PEG solution, a low precipitator temperature, and low molecular weight of the PEG. The phase behavior of the solution mixture in the saturator presented a qualitative relationship. At the optimized volumetric flow rate ratios, the composition of CO2 in the feed streams was near the bubble points of the saturator temperatures. X-ray and differential scanning calorimetry analyses indicated that LTSAA-treated PEG had a reduced degree of crystallinity, which could be modulated via the precipitator temperature. PEG microparticles prepared by a LTSAA process would be promising carriers for drug-controlled formulations of PEG-drug composite particles.

CONTROLLED RELEASE OF THEOPHYLLINE-CHITOSAN COMPOSITE PARTICLES PREPARED USING SUPERCRITICAL ASSISTED ATOMIZATION

Abstract This study investigated the formation of composite particles of chitosan (CS) and theophylline (TPH) via supercritical assisted atomization (SAA) using aqueous ethanol (50%, v/v) as the solvent and supercritical CO2 as the spraying medium. According to XRD, DSC, and FTIR analyses, the crystal form of the SAA-treated TPH from the as-received TPH was unchanged. The effect of different mass ratios of CS to TPH on the in vitro release of TPH showed that the dissolution of the highly water-soluble TPH was retarded when included in the composite particles and could be controlled by the mass ratio of the component in the SAA process. The in vitro dissolution data showed a good fit with the Peppas-Sahlin model, which was used to conclude that the drug release from the composite particles resulted from a combination of drug diffusion and relaxation of the polymer. As the mass ratio of CS to TPH increased, the mechanism relating to polymer relaxation became crucial in the TPH-CS composite particles.

Preparation of pH-responsive DOX-loaded chitosan nanoparticles using supercritical assisted atomization with an enhanced mixer

Chemotherapeutics are used extensively in cancer and encapsulating the drug in nanoparticles is an effective method to enhance therapeutic efficacy and reduce side effect. In this work, DOX-loaded chitosan nanoparticles were prepared using supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM) from aqueous solution. The influences of solution concentration, CO2/solution ratio, mixer pressure, chitosan/DOX ratio and chitosan molecular weight on particle morphologies and sizes were investigated in detail. Well defined spherical nanoparticles with average diameter ranging from 120 nm to 250 nm were obtained, and the loading efficiency was up to 90%. FT-IR result showed that the structure of DOX was not changed after the SAA-HCM process. Zeta potential of the nanoparticles was about +50 mV. The in vitro drug release behavior conducted in the media with pH of 4.5, 6.5 and 7.4 respectively showed strongly pH responsive. In vitro cytotoxicity profiles revealed that the activity of DOX was well maintained after loaded into chitosan nanoparticles. The SAA-HCM process was demonstrated to be a promising technique for one-step production of polymer/drug composite nanoparticles suitable for cancer drug delivery from aqueous solution.

Characterization and aerosolization performance of mannitol particles produced using supercritical assisted atomization

Different shapes and sizes of water-soluble mannitol (MAN) particles were prepared using a supercritical assisted atomization (SAA) process. The needle-shaped and spheroidal mannitol particles were prepared using water and aqueous ethanol, respectively, as solvent of the MAN solution. The size of mannitol particles increased with increasing the concentrations of MAN solution and deceased with increasing saturator temperatures and CO2-solution flow ratios. The in vitro aerodynamic behavior of the mannitol particles as dry powder inhaler (DPI) formulations was investigated using an Andersen cascade impactor. The effects of the morphology and the size of mannitol particle on powder deagglomeration and flowability were evaluated. In vitro aerosolization tests showed that the spheroidal particles favor deagglomeration of mannitol powder and the fine particle fraction (FPF) was enhanced by the excellent powder flowability of the larger mannitol microparticles.

Thermally triggered transition of fluid atomized micro- and nanotextured multiscale rough surfaces

Evaluation of fluid atomized spraying process parameters for poly(1,1,2,2-tetrafluoroethylene) coating such as ‘patternation’ influencing on the distribution of droplets inside the spray boundary, air pressure affecting the ‘nozzle flow-rate’, air pressure assisted nozzle flow rate dependent ‘droplet size’, etc. gives state-of-the-art hydrophobicity. The fabricated coating shows the transition from hydrophilic surface to hierarchical rough hydrophobic surface (WCA = 139° ± 3°) at a temperature of 130 °C. Furthermore, the reflex of transition temperature on the hydrophobicity of coated system triggers the fabrication of hierarchical surface morphology culminating the maximum static water contact angle (147° ± 3°) at an optimized temperature of 220 °C. Tailoring of nano-spindles over the multiscaled hierarchical rough surface by the synergistic effect of air-pressure assisted atomization parameters and thermally triggered transition temperature endowing ultimate hydrophobicity. Atomic force microscopy (AFM) characterization of the coating morphology confirms the triggered temperature by demonstrating the nano-spindled structure with RMS roughness (78 nm). Anti-corrosion performance of thermally triggered hydrophobic coating containing ‘air valleys’ has been evaluated by using Tafel polarization curves proclaiming reduction in corrosion rate (0.001 mmpy) in the coated system. The results obtained by the following study possess tremendous potential to tailor-wet characteristics of the nano-textured atomized PTFE coating for diversified naval applications.

Luteolin/dextran-FITC fluorescent microspheres produced by supercritical assisted atomization

Supercritical Assisted Atomization was used to produce a complex particulate system, consisting of a polysaccharide (Dextran, DEX) loaded with a fluorescent agent (Fluorescein isothiocyanate, FITC) and a poorly water soluble compound (Luteolin, LUT). Different LUT/(DEX+FITC) weight ratios and different concentrations were investigated to develop microparticles that can act as an imaging agent and as a drug delivery carrier. SAA produced spherical, well-separated and amorphous particles. Analytical studies revealed that LUT was uniformly dispersed in DEX matrix and specific interactions appeared between LUT and DEX. LUT loading efficiencies reached 100% and dissolution tests in a phosphate-buffered saline solution were up to 18 times faster compared to the physical mixture, due to an efficient dispersion of LUT in DEX matrix and to the formation of hydrogen bonds between LUT and DEX. All results confirmed that the presence of FITC in SAA coprecipitates did not influence particle size, morphology and LUT dissolution rate.

Modeling of the Behavior of Natural Polysaccharides Hydrogels for Bio-pharma Applications

Hydrogels, even if not exclusively obtained from natural sources, are widely used for pharmaceuticals and for biomedical applications. The reasons for their uses are their biocompatibility and the possibility to obtain systems and devices with different properties, due to variable characteristics of the materials. In order to effectively design and produce these systems and devices, two main ways are available: i) trial-and-error process, at least guided by experience, during which the composition of the system and the production steps are changed in order to get the desired behavior; ii) production process guided by the a-priori simulation of the systems’ behavior, thanks to proper tuned mathematical models of the reality. Of course the second approach, when applicable, allows tremendous savings in term of human and instrumental resources. In this mini-review, several modeling approaches useful to describe the behavior of natural polysaccharide-based hydrogels in bio-pharma applications are reported. In particular, reported case histories are: i) the size calculation of micro-particles obtained by ultrasound assisted atomization; ii) the release kinetics from core-shell micro-particles, iii) the solidification behavior of blends of synthetic and natural polymers for gel paving of blood vessels, iv) the drug release from hydrogel-based tablets. This material can be seen as a guide toward the use of mathematical modeling in bio-pharma applications.

Production of Luteolin/Biopolymer Microspheres by Supercritical Assisted Atomization

Supercritical assisted atomization (SAA) was used to produce coprecipitated submicroparticles of luteolin (LUT)/poly(vinylpyrrolidone) (PVP) for pharmaceutical applications. LUT has antioxidant, antiinflammatory, and antitumoral properties but is poorly water-soluble, whereas PVP is highly water-soluble. This polymer can be used to protect the active molecule and to improve its bioavailability. Different LUT/PVP weight ratios were selected ranging between 1:4 and 1:8. SAA produced partly collapsed spherical particles with controlled particle size and mean diameters ranging between 0.22 and 0.33 μm. UV–vis analyses revealed very high loading efficiency of LUT in SAA particles (99–100%). The powders are amorphous, whereas the untreated material shows crystalline patterns. Fourier transform infrared revealed that hydrogen bonds were created between the drug and polymer. Drug-release analysis indicated that the supercritical processing was successful: the LUT dissolution rate in a phosphate-buffered saline so...

Dissolution enhancement of indomethacin-chitosan hydrochloride composite particles produced using supercritical assisted atomization

This study investigated the formation of drug-carrier composite particles via a supercritical assisted atomization (SAA) process using 50% (v/v) aqueous ethanol as a solvent, and carbon dioxide as a spraying medium. Indomethacin (IMC), a poorly water-soluble drug, was used as a model drug and chitosan hydrochloride (CH), a water-soluble carrier, was used as a carrier for composite particles. The effects of size and different CH to IMC weight ratios in the composite particles on drug dissolution rate were investigated. XRD, DSC and FTIR analyses showed that the SAA-treated IMC transformed from γ-form (as-received IMC) to the meta-stable α-form. In vitro dissolution test showed that the IMC dissolution rate was enhanced because of the transformation in crystalline form, increased drug wettability due to water-soluble CH in composite particles, and high surface area due to the decreased size of composite particles. Furthermore, the composite particles demonstrated enhanced drug permeability in Caco-2 cell monolayer. Taken together, the enhanced permeability and dissolution rate could be beneficial for the bioavailability of active pharmaceutical ingredients (APIs).

Precipitation kinetics and biological properties of chitosan microparticles produced using supercritical assisted atomization

In this study, the formation of sub-micrometric chitosan (CS) particles via supercritical assisted atomization (SAA) was investigated using supercritical CO2 spraying medium and aqueous ethanol solution (50%, v/v) as solvent. Results indicated that smaller CS particle were obtained by using low concentrations of the CS solution, high saturator temperatures, and an optimized CO2-to-CS solution flow ratio. Using the mixed-suspension, mixed-product-removal (MSMPR) population balance model, the precipitation kinetics parameters were determined from CS particle size distributions and the mass-weighted mean sizes of CS particles, which are a function of the precipitation parameters. An efficient tight junction opening effect was induced by the interaction of CS microparticles and Caco-2 cell monolayers as indicated by the marked decrease in the transepithelial electrical resistance (TEER) of Caco-2 cell monolayers incubated with CS particle suspensions. In addition, the reversibility of the TEER changed depending on the viability of the Caco-2 cells, and cell viability was high at low concentrations of CS suspensions.