Bubble Properties Research Articles

Acoustic Bubble and Magnetic Actuation-Based Microrobot for Enhanced Multiphase Drug Delivery Efficiency.

This paper proposes an acoustic bubble and magnetic actuation-based microrobot for enhancing multiphase drug delivery efficiency. The proposed device can encapsulate multiphase drugs, including liquids, using the two bubbles embedded within the microtube. Additionally, using the magnetic actuation of the loaded magnetic liquid metal, it can deliver drugs to target cells. This study visualized the flow patterns generated by the oscillating bubble within the tube to validate the drug release principle. In addition, to investigate the effect of the oscillation properties of the inner bubble on drug release, the oscillation amplitude of the inner bubble was measured under various experimental variables using a high-speed camera. Subsequently, we designed a microrobot capable of encapsulating bubbles, drugs, and magnetic liquid metal and fabricated it using microfabrication technology based on ultra-precision 3D printing. As a proof of concept, we demonstrated the transport and drug release of the microrobot encapsulating the drug in a Y-shaped channel simulating a blood vessel. The proposed device is anticipated to enhance the efficiency of drug therapy by minimizing drug side effects, reducing drug administration frequency, and improving the stability of the drug within the body. This paper is expected to be applicable not only to targeted drug delivery but also to various biomedical fields, such as minimally invasive surgery and cell manipulation, by effectively delivering multiphase drugs using the simple structure of a microrobot.

Linking polymer architecture to bubble shape in LDPE film blowing through multistage modeling

To meet the challenge of efficient modeling of film blowing with realistic constitutive equations for commercial thermoplastic melts, we present a multistage optimization modeling framework that integrates polymerization reaction modeling, rheology modeling, and bubble-shape prediction. A direct link is thereby created between the polymer architecture and the bubble shape of low-density polyethylene (LDPE) through a three-stage modeling protocol. Stage 1 aims to get complete polymer structure information from a limited set of linear and nonlinear rheological data and the measured averaged molecular weight. An optimization loop uses the Tobita algorithm for polymer reaction and the BoB model for rheology to minimize the deviation between experimental data and model predictions. Stage 2 is designed to obtain a representative reduced ensemble of LDPE in the Rolie-double-poly (RDP) model to reduce the computational cost of rheology calculations during processing. The parameters of the reduced molecular components are obtained by fitting the RDP model to a wide range of rheology data predicted by the BoB model applied to the full ensemble of polymer architectures obtained in stage 1. In stage 3, the reduced-ensemble RDP model is coupled to measured temperature profiles using time–temperature superposition, and the bubble shape and strain rate history of a fluid particle in the bubble are obtained by minimizing error in the momentum balance equations. We show that each stage of the process yields successful fitting, and at the end, we obtain an a priori prediction of height-dependent bubble radius and velocity in agreement with experiment. With this multistage optimization strategy, we link the polymer compositions to the bubble properties during the film blowing of LDPE.

Effect of frother on bubble entraining particles in coal flotation

Understanding the effect of frother on bubble entraining coal particles is an important guidance for regulating coal flotation behavior. The bubble properties and the flow field surrounding the bubble were investigated using the particle image velocimetry (PIV) technique. The bubble equivalent diameter, bubble deformation rate and low-velocity region area reduced as the frother concentration increased due to a decrease in surface tension. The oscillation of the bubble and low-velocity region were subsequently analyzed. As the frother concentration increased, the oscillation frequency of the bubble and low-velocity region gradually decreased until 1.6 × 10−4 mol/L after that it tended to be stable. The oscillation amplitude of the bubble and low-velocity region slightly varied with the frother concentration but increased as the distance away from the bubble increased. The coal particle trajectories and entrainment phenomenon under the effect of frother were explored via the high-speed motion acquisition equipment. Three typical trajectories that Escape, Offset entrainment, and Entrainment were used to describe the coal particle behavior around the bubble. A predictive model of coal particle entrainment probability influenced by frothers was established. Our findings can provide valuable insight into the development of technology for mineral flotation.

Experiment and Simulation Study of the Laser-Induced Cavitation Bubble Technique for Forming a Microgroove in Aluminum Foil.

The present work introduces a laser-induced cavitation bubble technique for forming an axisymmetric structure (i.e., microgroove) and the dynamics of a cavitation bubble from initial expansion to the collapse stages that were also simulated. Furthermore, the shock wave signals and dynamic properties of the cavitation bubble were recorded using a hydrophone and a high-speed camera. The experiments on microgrooves formed by laser-induced cavitation bubble stamping were carried out, and the effects of laser energy, the initial position of the bubble, and the number of impacts on the microformability of aluminum sheets are discussed. The depth of the microgroove was investigated using experiments, and it was found that the process can serve as a rapid technique for impressing microfeatures on thin-sheet metals. The experimental results showed that as the initial position of the bubble increased, the deformation depth decreased. As the laser energy and number of impacts increased, the deformation depth increased. The results of the response surface experiments showed that a laser energy of 27 mJ, 3 impacts, and a bubble position of 3 mm were optimal for the process. By using the optimal parameters, flat and smooth microgrooves with a forming depth of 102.54 µm were successfully fabricated. Furthermore, the maximum thickness thinning of the microgroove section occurred at the entrance areas, and this area had the greatest hardness. This also indicated that the greatest amount of plastic deformation of the material and grain refinement occurred in this area. On the other hand, the aluminum foil did not undergo oxidation during the plastic deformation process. These results demonstrated that laser-induced bubble stamping is an advanced micromachining method with promising applications.

Ultrasound-enhanced adsorption of amino acids from aqueous solution onto macroporous resins for green separation: Mass transfer mechanism and acoustic cavitation properties

The utilization of green technology for the recovery of renewable components has garnered significant attention. In this study, efficient and rapid separation of amino acids from aqueous solutions was achieved through ultrasound-assisted macroporous resin adsorption. The numerical simulation revealed the underlying mechanism of mass transfer during ultrasound-assisted adsorption and clarified the impact of acoustic properties on the adsorption process. Low-frequency (LFUS, 20 kHz) caused the damage of resin structure and the increase of adsorption capacity whereas these were less influenced by high-frequency ultrasound (HFUS, 1056 kHz). The external mass transfer coefficient was increased by 161% and 45% during LFUS- and HFUS-assisted adsorption than agitation-assisted adsorption. In addition, both US modes contributed to an enhancement of surface diffusion coefficient by over 100%. The predominant factor governing the intraparticle diffusion for amino acid adsorption was found to be pore volume diffusion, accounting for more than 70% of the overall process. Both LFUS and HFUS were observed to augment the influence of surface diffusion within the overarching diffusion phenomenon, aligning with the concurrent elevation of the surface diffusion coefficient. Furthermore, the mechanism of ultrasound-assisted adsorption was illustrated from the aspect of physical and sonochemical effects generated by the acoustic cavitation. The accumulated acoustic pressure of LFUS exceeded that of HFUS by a factor of 105, reflecting its strong physical effects. The connection between the mass transfer behaviour and acoustic bubble properties during ultrasound-assisted adsorption can provide guidance for the industry to apply ultrasound as a green technology to separate and recover renewable biomaterials from wastewater.

Comparison of bubble parameters in natural and chemical surfactant solutions: a force analysis

The authors have investigated the potential of a plant-based natural surfactant in the modification of various bubble parameters. Bubble dynamics at the orifice were studied in natural surfactant solutions extracted from the plant Sapindus mukorossi at concentrations below and above its critical micellar concentration (CMC). The results were compared to the ones obtained with Sodium Dodecyl Sulfate solutions. The CMC values of Sapindus mukorossi and Sodium Dodecyl Sulfate are 7.5 × 10−3 g/cc and 2.39 × 10−3 g/cc, respectively. A photographic method was employed to observe bubble formation at the orifice. The results show that biosurfactants, like chemical surfactants, have a comparable effect on bubble density, size, and rise velocity. Experimentally determined bubble radius, volume, and radial velocity were used to calculate various forces contributing to the bubble dynamics. The buoyancy, pressure, and surface tension forces were significantly stronger in magnitude in comparison to the gas momentum, viscous drag, and added mass forces. Our findings suggest that the significance of various dynamic forces involved in bubble growth dynamics varies according to the bubble generation frequency regimes. We report for the first time the potential of Sapindus mukorossi in altering bubble properties and surface forces at the orifice and its usage in various bubble-related industrial applications.

Analysis of sound emissions and physical properties of bubbles generated by breaking waves

Although the relationship between bubble diameter and the corresponding resonant frequency has been known since 1930s, the link between the amplitude of the sound and the physical properties of the bubble is still unclear. Sound amplitude is a parameter inevitably measured when passive acoustic measuring techniques are employed, and its magnitude as measured is related to not only the size of the bubble but also its position in space relative to the measurement point. Here, we present a study where individual bubbles were first generated through a vertical plunging jet and analyzed to establish a link between their diameters and sound emissions. Subsequently, these data were used to predict bubble properties occurring in breaking waves generated in laboratory experiments. A high frequency camera was used to capture images of the bubbles and visually check the accuracy of the diameter and location predictions. Results show good agreement between plunging jet and breaking waves bubbles within the +− 1.5 dB confidence interval; addressing with residual experimental uncertainties should offer further improvements.

Study of bubble behavior in a gas–solid dense-phase fluidized bed based on deep learning

Fluidization characteristics and hydrodynamics of gas–solid fluidized beds are controlled by bubble properties. However, the existing conventional image segmentation methods are unable to effectively resolve the problems of overlap and background interference between small bubbles, and the segmentation performance for bubbles must still be enhanced. To study the bubble behavior of a gas–solid dense-phase fluidized bed, a two-dimensional fluidized bed with different air distributors was adopted. The application of deep learning to digital image analysis technology is to improve the precision and automation of bubble recognition. The DeepLab V3+ model incorporates multi-scale information, which is well-compatible with uncertain bubble boundary information while enhancing the segmentation effect. A pixel accuracy of 97.95% and a mean intersection over union (MIoU) of 80.91% for multi-group bubble image segmentation were achieved. In comparison to conventional threshold-based recognition methods, the accuracy of the deep learning method increased by up to 40.31% and the MIoU by up to 53.88%, demonstrating the great potential and application value of semantic segmentation in the study of the complex motion behavior of gas–solid sorting fluidized bed bubbles. The influence of the air distributor on the behavior of bubbles is verified. The results indicate that air distributor aperture directly influences bubble diameter, aspect ratio, and shape factor, with coalescence being the primary cause of bubble enlargement.

Synergistic Effect of Frequently Found Ions in the Flotation of Pb-Zn Sulfide Ores on Air/Water Interface

The aqueous ions influence the properties of air bubbles and, therefore, the recovery of flotation. This study aims to reveal the synergistic effect of frequently found ions in the flotation of Pb-Zn sulfide ores. In this context, dynamic surface tension measurements, bubble coalescence time, Sauter mean diameter (SMD), bubble size distribution (BSD), and dynamic foam stability (DFS) measurements were carried out using artificial process waters (APWs). APW with the minimum ion concentration is expressed as “APW1” with the ionic strength (I) of 0.03 mol/dm3. The concentration of the ions in APW1 was increased by 3, 5, and 10 times, and thus APW3 (I = 0.08 mol/dm3), APW5 (I = 0.13 mol/dm3), and APW10 (I = 0.26 mol/dm3) were prepared, respectively. The results of this study indicated that the surface tension increased slightly in the presence of APW related to the ion concentration. Potassium ethyl xanthate (KEX) at high concentrations was effective in the reduction of surface tension. As the APW concentration increased, finer bubbles were obtained with a narrower size range. The stability of the foam increased with butyl glycol (BG) and APW concentration. There was no need to use a frother (BG) for the flotation experiments in the presence of APW1 or APWs with higher ionic strength.

Bubble manipulates the release of viral aerosols in aeration

Bubble bursting is a common phenomenon in many industrial and natural processes, plays an important role in mediating mass transfer across the water-air interface. But the interplay between bubbles and pathogens remains unclear and the mechanisms of virus aerosolization by the bubble properties have not been well studied. The main objective of this study was to evaluate the water-to-air transfer of viruses by bubbles of different sizes. Unlike the dominant view of smaller bubbles less bioaerosols, it was found that the smaller bubbles could generate significantly more viral aerosols regardless of the virus species (Phi6, MS2, PhiX174, and T7), when the Sauter mean bubble diameters were between 0.56 and 1.65 mm under constant aeration flow rate. The mechanism studies denied the possibilities of more aerosols or better dispersion of viruses in the aerosols generated by the smaller bubbles. However, deeper bubbling could transfer more viruses to the air for MS2, PhiX174, and T7. Their concentrations in aerosols were linearly related to the bubbling depth for these non-enveloped viruses, which demonstrates the bubble-scavenging effect as a main mechanism except for the enveloped virus Phi6. Whereas, unlike these three non-enveloped viruses, Phi6 could survive relatively better in the aerosols generated from the smaller bubbles, though the enhancement of aerosolization by the smaller bubbles was much larger than the improvement of survival. Other mechanisms still remain unknown for this enveloped virus. This study suggests that the attempt of decreasing the bubble size in aeration tank of the wastewater treatment plant might significantly increase the solubility of oxygen as well as the risk of viral aerosols.

Effect of Low–Frequency Vibrations on the Hydrodynamic Properties of Single Bubbles at Different Gravity Levels

Effect of Low–Frequency Vibrations on the Hydrodynamic Properties of Single Bubbles at Different Gravity Levels

Bubble Behavior and Anode Effect on Different Carbon Anode Designs in Cryolite Melt Applying a See-through Furnace

Anodic CO2 gas evolution is one of the main processes in the Hall-Héroult electrolysis cell for primary aluminium production. This work is a laboratory scale study of the effect of anode geometry, anode orientation and carbon anode material on bubble behavior and bubble properties in cryolite melt. Increased knowledge of the bubble behavior is important for improved design of industrial cells, but also for laboratory‐scale experiments. The anodes studied in this work are frequently applied for investigation of reaction kinetics and mass transport, anode effect, current efficiency, anode quality properties, etc. It is therefore of interest to study the bubble dynamics of these anodes in more detail because bubble evolution is relevant for all the above-mentioned phenomena.The anode potential has been shown to be highly dependent on anode geometry and orientation. For this study four different anode designs were made: horizontal (downward-facing), inverted horizontal (upward-facing), vertical, rod (with both vertical and horizontal surface). For most of the designs, characteristics such as bubble noise, bubble size, and wetting were obtained as a function of current density or anode potential/cell voltage. The bubble noise normally went through a maximum, while the bubble size decreased in the whole current density range. The wetting contact angle showed little variation with current density. It was assumed that the current density had a stronger effect on the contact angle through its effect on the bubble size than the polarization and associated surface roughening.Also, phenomena like nucleation, growth, coalescence, bubble detachment and anode effect were studied for both graphite and industrial carbon as anode material. The nucleation was more pronounced at the industrial carbon due to more active sites confirmed by CT analysis. The coalescence process was found to be independent of current density/potential and carbon anode material and was in the range 16-24 msec. On increased currents anode effect occurred on both anodes, the current being lower for the graphite anode at onset. Video recordings and electrochemical measurements showed more abrupt initiation of the anode effect on the graphite and a strong de-wetting of the anode. With the existence of a (C – F) surface compound on the anode, as long as the anode effect gas could escape the electrode surface, the anode seems to be electrochemically active towards both CO/CO2 and PFC formation during anode effect.In addition to the bubble characteristics and phenomena described, the impact of the results for better anode design for laboratory scale studies is discussed.

Enhanced treatment of azo dyes in wastewater using heat-activated persulfate with micro-nano bubble aeration

Azo dyes-containing wastewater can lead to environmental issues and pose threats to public health. The efficient degradation of azo dyes with novel and potent techniques, remains a challenge. This study presented an innovative utilization of micro-nano bubble aeration technology to improve the treatment of Rhodamine B through heat-activated persulfate oxidation. Through single factor experiments, the impacts of persulfate concentration, temperature, initial Rhodamine B concentration, and pH values were systematically explored on the degradation of Rhodamine B in heat-activated persulfate oxidation. The removal rate of Rhodamine B was 94.53% optimized by Response surface optimization method. The reaction rate was in the range of 0.0109–0.0528 min−1, governed by pseudo-first-order kinetics. By applying the Arrhenius equation, the activation energy was determined to be 14.06 KJmol−1. Furthermore, properties of micro-nano bubbles and their synergistic coefficient were investigated in heat-activated persulfate oxidation. Quenching tests revealed the predominance of sulfate radicals, and full wavelength scanning facilitated an in-depth investigation of the reaction mechanism. Additionally, a proposed electron shell structure elucidated the decomposition process of Rhodamine B. Therefore, the implementation of micro-nano bubble aeration technology based on heat-activated persulfate oxidation, held the promise as an efficient and effective approach for the treatment of printing and dyeing wastewater.

Harmful algal bloom aerosols and human health.

Harmful algal blooms (HABs) are increasing across many locations globally. Toxins from HABs can be incorporated into aerosols and transported inland, where subsequent exposure and inhalation can induce adverse health effects. However, the relationship between HAB aerosols and health outcomes remains unclear despite the potential for population-level exposures. In this review, we synthesized the current state of knowledge and identified evidence gaps in the relationship between HAB aerosols and human health. Aerosols from Karenia brevis, Ostreopsis sp., and cyanobacteria were linked with respiratory outcomes. However, most works did not directly measure aerosol or toxin concentrations and instead relied on proxy metrics of exposure, such as cell concentrations in nearby waterbodies. Furthermore, the number of studies with epidemiological designs was limited. Significant uncertainties remain regarding the health effects of other HAB species; threshold dose and the dose-response relationship; effects of concurrent exposures to mixtures of toxins and other aerosol sources, such as microplastics and metals; the impact of long-term exposures; and disparities in exposures and associated health effects across potentially vulnerable subpopulations. Additional studies employing multifaceted exposure assessment methods and leveraging large health databases could address such gaps and improve our understanding of the public health burden of HABs.

Modeling sea ice albedo and transmittance measurements with a fully-coupled radiative transfer model.

A rigorous treatment of the sea ice medium has been incorporated in the advanced Coupled Ocean-Atmosphere Radiative Transfer (COART) model. The inherent optical properties (IOPs) of brine pockets and air bubbles over the 0.25-4.0 µm spectral region are parameterized as a function of the sea ice physical properties (temperature, salinity and density). We then test the performance of the upgraded COART model using three physically-based modeling approaches to simulate the spectral albedo and transmittance of sea ice, and compare them with measurements collected during the Impacts of Climate on the Ecosystems and Chemistry of the Arctic Pacific Environment (ICESCAPE) and the Surface Heat Budget of the Arctic Ocean (SHEBA) field campaigns. The observations are adequately simulated when at least three layers are used to represent bare ice, including a thin surface scattering layer (SSL), and two layers to represent ponded ice. Treating the SSL as a low-density ice layer yields better model-observation agreement than treating it as a snow-like layer. Sensitivity results indicate that air volume (which determines the ice density) has the largest impact on the simulated fluxes. The vertical profile of density drives the optical properties but available measurements are scarce. The approach where the scattering coefficient for the bubbles is inferred in lieu of density leads to essentially equivalent modeling results. For ponded ice, the albedo and transmittance in the visible are mainly determined by the optical properties of the ice underlying the water layer. Possible contamination from light-absorbing impurities, such as black carbon or ice algae, is also implemented in the model and is able to effectively reduce the albedo and transmittance in the visible spectrum to further improve the model-observation agreement.

Numerical simulation of dynamic characteristics of hydrofoil structure under cavitation conditions

In this paper, the effects of different cavitation bubble on the natural frequency, mode shape and hydrodynamic damping of the NACA0009 hydrofoil are investigated by numerical simulation method. The cantilever truncated hydrofoil model is set in a high-speed water tunnel. The dynamic characteristics of the hydrofoil structure is affected by the fluid-structure coupling. Compared to the properties of water, the density of cavitation bubbles decreases, causing an increase in the natural frequency of the structure, and the decrease in the speed of sound also causes a change in the mode shape. The growth rate of frequency under unit chord length cavitation is nonlinear as the cavitation bubble length increases. By defining a modal displacement function to compare the structural mode shapes, cavitation intensifies the bending and torsional deformation of the hydrofoil. Even if the volume of cavitation bubbles is small, the inhomogeneous distribution of acoustic pressure and changes in cavitation bubble properties can cause changes in the structural mode shapes. The one-way FSI numerical method for hydrodynamic damping in cavitating flow is established and the applicability of this method is verified by the calculation of damping in water. For the first bending mode fc1, the hydrodynamic damping with 50% chord length (0.5lc) stably attaching cavitation is simulated. As the length of the cavitation bubble increases to 0.8lc, the damping value becomes smaller. The research in this paper lays the foundation for analysing the dynamic characteristics of hydraulic machinery with cavitation using numerical simulation method.

Investigation of Bubble Properties in a Bubbling Fluidized-Bed Gasification Reactor Using a Computational Particle Fluid Dynamic Model

Investigation of Bubble Properties in a Bubbling Fluidized-Bed Gasification Reactor Using a Computational Particle Fluid Dynamic Model

Thermal and chemical properties of the eROSITA bubbles from Suzaku observations

Thermal and chemical properties of the eROSITA bubbles from Suzaku observations

Underwater Wireless Optical Communication System Channel Modelling With Oceanic Bubbles and Water Constituents Under Different Wind Conditions

Optical wireless data transmission from an autonomous underwater vehicle (AUV) to a sea-surface buoy has become a viable solution to support the increasing needs for many applications in the field of marine technology. Despite having unique characteristics and advantages, underwater wireless optical communication remains a challenging field due to the difficulties associated with the harsh marine environments and severe attenuation caused by the bubbles and particulates. This study aims to evaluate the uplink UWOC system in the presence of particles and bubbles under various wind speeds. To calculate the link distances and signal loss between a transmitter and a receiver of the UWOC system, simulations were performed with the inputs of the water optical properties obtained from the Bay of Bengal and Southern Ocean waters and bubble properties derived from the Hall-Novarini (HN) model. Consequently, the normalized received power were calculated for the different receiver configurations and oceanic conditions without and with bubbles. Our results showed that the received power decreased with the increasing wind speeds and smaller bubble populations. The angular and spatial distributions of the received beam increased for smaller bubble populations under high wind speeds. When compared to the clean bubbles, the received power slightly decreased for the non-absorbing coated bubbles with different film thicknesses (0.01 ∼ 1.0 μm) and increased for the absorbing coated bubbles with higher thicknesses (≥1 μm). These results will significantly help the system designer to develop and optimize an UWOC system under different bubble populations and wind speed conditions.

Micromechanical properties of spherical and facetted He bubble loaded copper

Exploring new irradiation resistant materials requires understanding their mechanical responses to irradiation. Resistance to helium bubble formation and understanding bubble effects on the mechanical response of candidate materials are crucial factors to qualify materials as irradiation resistant. Here, we explore the effect of spherical and facetted helium bubbles on the mechanical response of copper via in-situ micromechanical tensile testing at room temperature. Bubble formation and shape effects on strength and ductility, and their behavior on grain boundaries are discussed and compared to literature. Loading Cu with helium bubbles is shown here to increase strength but decrease ductility.