Microbubble Formation Research Articles

Microbubbles with optical fiber tips chemically worn

This research shows an experimental study and analysis on microbubbles formation, through the use of chemically modified optical fiber tips. Microbubbles are formed in highly absorbent liquid using a continuous wave laser at 980 nm, with conventional powers. This report is considered, as the first study and dynamic analysis for microbubble formation in solution with these particular types of tips. Fiber tips are modified by the chemical wear method, using hydrofluoric acid, while, microbubbles are generated with the help of the deposition or adhesion of nanostructures on the modified tips. We have used carbon nanotubes dissolved in ethanol as nanostructures. We present an analysis of the results considering: the growth curves of the microbubbles, the largest radii, the lifetime and the growth rate. Finally, we discuss the important features of results, suggesting a possible way to control the size and number of microbubbles. Furthermore, the results of our research could be useful to improve the proposals of earlier applications or to propose new ones. The results shown can be useful for new applications or to improve proposals.

In Situ Shape Control of Thermoplasmonic Gold Nanostars on Oxide Substrates for Hyperthermia-Mediated Cell Detachment.

Gold nanostars (AuNSTs) are biocompatible, have large surface areas, and are characterized by high near-infrared extinction, making them ideal for integration with technologies targeting biological applications. We have developed a robust and simple microfluidic method for the direct growth of anisotropic AuNSTs on oxide substrates including indium tin oxide and glass. The synthesis was optimized to yield AuNSTs with high anisotropy, branching, uniformity, and density in batch and microfluidic systems for optimal light-to-heat conversion upon laser irradiation. Surface-enhanced Raman scattering spectra and mesoscale temperature measurements were combined with spatially correlated scanning electron microscopy to monitor nanostar and ligand stability and microbubble formation at different laser fluences. The capability of the platform for generating controlled localized heating was used to explore hyperthermia-assisted detachment of adherent glioblastoma cells (U87-GFP) grafted to the capillary walls. Both flow and laser fluence can be tuned to induce different biological responses, such as ablation, cell deformation, release of intracellular components, and the removal of intact cells. Ultimately, this platform has potential applications in biological and chemical sensing, hyperthermia-mediated drug delivery, and microfluidic soft-release of grafted cells with single-cell specificity.

Near-perfect microlenses based on graphene microbubbles

Microbubbles acting as lenses are interesting for optical and photonic applications such as volumetric displays, optical resonators, integration of photonic components onto chips, high-resolution spectroscopy, lithography, and imaging. However, stable, rationally designed, and uniform microbubbles on substrates such as silicon chips are challenging because of the random nature of microbubble formation. We describe the fabrication of elastic microbubbles with a precise control of volume and curvature based on femtosecond laser irradiated graphene oxide. We demonstrate that the graphene microbubbles possess a near-perfect curvature that allows them to function as reflective microlenses for focusing broadband white light into an ultrahigh aspect ratio diffraction-limited photonic jet without chromatic aberration. Our results provide a pathway for integration of graphene microbubbles as lenses for nanophotonic components for miniaturized lab-on-a-chip devices along with applications in high-resolution spectroscopy and imaging.

Effectiveness of Oil-Layered Albumin Microbubbles Produced Using Microfluidic T-Junctions in Series for In Vitro Inhibition of Tumor Cells.

This work focuses on the synthesis of oil-layered microbubbles using two microfluidic T-junctions in series and evaluation of the effectiveness of these microbubbles loaded with doxorubicin and curcumin for cell invasion arrest from 3D spheroid models of triple negative breast cancer (TNBC), MDA-MB-231 cell line. Albumin microbubbles coated in the drug-laden oil layer were synthesized using a new method of connecting two microfluidic T-mixers in series. Double-layered microbubbles thus produced consist of an innermost core of nitrogen gas encapsulated in an aqueous layer of bovine serum albumin (BSA) which in turn, is coated with an outer layer of silicone oil. In order to identify the process conditions leading to the formation of double-layered microbubbles, a regime map was constructed based on capillary numbers for aqueous and oil phases. The microbubble formation regime transitions from double-layered to single layer microbubbles and then to formation of single oil droplets upon gradual change in flow rates of aqueous and oil phases. In vitro dissolution studies of double-layered microbubbles in an air-saturated environment indicated that a complete dissolution of such bubbles produces an oil droplet devoid of a gas bubble. Incorporation of doxorubicin and curcumin was found to produce a synergistic effect, which resulted in higher cell deaths in 2D monolayers of TNBC cells and inhibition of cell proliferation from 3D spheroid models of TNBC cells compared to the control.

Phase Contrast Imaging Based Microbubble Monitoring of Radiofrequency Ablation: An ex vivo Study.

BackgroundTo explore the potential of synchrotron radiation (SR) phase contrast imaging (PCI) for real-time microbubble formation monitoring during radiofrequency ablation (RFA).MethodsRFA was performed on ex vivo porcine muscle tissue using unipolar and multi-tined expandable electrodes. Images of microbubble formation in the samples were captured by both SR PCI and absorption contrast imaging. The synchronous ablation temperature was recorded. Each RFA electrode type group contained 6 samples. Ablation size was assessed by histologic examination.ResultsMicrobubble formation during RFA could be visualized by SR PCI. The diameter of the microbubbles revealed on the image ranged from tens of microns to several millimeters, and these microbubbles first appeared at the edge of the RFA electrode when the target region temperature reached approximately 60°C and rapidly extended outwards. The average microbubble range measured on PCI was 17.66 ± 0.74 mm. The average range of coagulation necrosis measured by histological examination was 17.22 ± 0.38 mm. There was no significant difference between them (P > 0.05). The range of microbubbles corresponded to the ablation zone.ConclusionPCI enabled real-time high-resolution visualization of microbubble formation during RFA, indicating a potential for its use in ablation monitoring.

Fluorocarbon Gas Exposure Induces Disaggregation of Nanodiamond Clusters and Enhanced Adsorption, Enabling Medical Microbubble Formation

Introducing fluorocarbon vapor in the air above an aqueous dispersion of clusters of nanodiamonds induces their disaggregation, a prerequisite for most of their biomedical uses. Furthermore, the fl...

Study of 3D-Printed Pressure Release Nozzle for Microbubble Formation in Full-Scale Dissolved Air Flotation (DAF)

Pressure-release equipment for the formation of microbubbles is an important part of any DAF system. In this study, 3D printing was employed to produce new nozzles, followed by testing to find the optimum pressure and flowrate. The flowrate through the nozzle affected both the empty bed residence time (EBRT) of the saturator and also the nucleation of bubbles. With the increase of flow rate, the total number of bubbles was seen to increase. This is a significant observation meaning that the enhanced precipitation of bubbles outweighs the reduced EBRT. This fact can improve equipment sizing and reduce CAPEX. Meanwhile, DAF is a technology that can help extend membrane life and reduce operational issues in seawater reverse osmosis (SWRO). So for further validation, a full-scale DAF was built and tested for SWRO pretreatment on the coast of the Persian Gulf. The system was tested with/without coagulation as well as with/without filtration media embedded inside the DAF tank. The results showed that the use of coagulation alongside DAF reduced the turbidity by more than 60% while using a DAF with embedded filtration could reduce the turbidity to less than 1 NTU. In comparison to common media filters, the proposed setup showed better performance.

Study on the coloring mechanism of the Ru celadon glaze in the Northern Song Dynasty

The Ru kiln is one of the five most famous kilns in the Chinese Song Dynasty. To clarify the coloring mechanism of the Ru celadon glaze, the celadon samples from the Ru Guan kiln site of Qingliangsi were analyzed by spectrophotometer, X-ray fluorescence spectrum, Raman spectroscopy, scanning electron microscopy and X-ray photoelectron spectrum. The results indicated that the molar ratios of SiO2/Al2O3 and CaO/(CaO + Al2O3) affected the formation of micro-bubbles, anorthite crystals and phase separated structures. A large number of bubbles and anorthite crystals formed special glossiness and opacifying effect in the Ru celadon glaze. And then, dense phase separation droplets in the amorphous region were in short-range order, but their diameters (31–46 nm) were too small to form visible structural colors on glaze surfaces. Only “opal effect” was formed by the light scattering, which added the aesthetic feeling for the Ru celadon. Besides, the phase separation droplets intensified the segregation of iron, and thus deepened the chemical color and made the Ru celadon glaze appear green-blue. Due to the neutral to alkaline soil at the Ru Guan kiln site, the water in the soil and its corrosion on the Ru celadon glaze resulted in the formation of Si–OH bond.

Ultrasonication to reduce particulate matter generated from bursting bubbles: A case study on zinc electrolysis

Particulate matters (PM) generated from bursting bubbles during electrolysis are hazardous and undesirable. Cleaner production technologies to reduce these PM by controlling bubble characteristics need to be explored. This study applied an ultrasonication method to reduce PM generated from zinc electrolysis. The results showed that the reduction efficiencies for total suspended particulates increased with the increase in ultrasonic power. The reduction mechanism was also investigated from the perspective of behavior of the bubble. The results showed that the number and size of microbubbles were both inversely related to the ultrasonic power, while positively related to the total mass of PM. Ultrasonication reduced PM by decreasing the number and size of microbubbles in two steps: i) during gas generation, ultrasonication inhibited anodic oxygen evolution and cathodic hydrogen evolution to reduce the gas amount; ii) after the formation of microbubbles, the mechanical effects of ultrasonication probably prematurely detach the microbubbles on electrode and directly burst microbubbles in electrolyte. Moreover, ultrasonication was also beneficial for increasing the current efficiency of zinc deposition and for lowering the energy consumption. The findings provided indications for ultrasonication technology to reduce PM from electrolysis and paved the road for exploring other clean PM reduction methods.

Combined method for acoustic cavitation research

At present, the field of applications of powerful ultrasound is expanding intensively, and the improvement of equipment and technological processes continues. With that, the key factor in the effect of ultrasonic vibrations on processes in liquids and liquid-like media is cavitation, i.e. the phenomenon of formation, pulsation and collapse of gas microbubbles under the influence of variable pressure. The widespread introduction of promising ultrasound technologies is largely constrained by the fact that the patterns of cavitation generation are not well understood, and the data known in the literature are contradictory and are characterized by low reproducibility. This paper describes an innovative method for studying ultrasonic cavitation. In order to increase the reproducibility of the results and the reliability of the conclusions about the correlation of various cavitation effects, it is proposed to register simultaneously the parameters characterizing these effects. An installation designed to implement this method has been developed and tested. The installation provides the ability to register the full output signal of the hydrophone, the intensity of the glow generated in the cavitation region - sound luminescence, the cavitation noise spectrum and its individual components. Technical characteristics of the installation allow you to adjust the rate of development of the cavitation region by varying the duration and period of the ultrasound pulses. It is possible to conduct experiments both in low-frequency (LF) and high-frequency (HF) fields as well as in interacting HF and LF ultrasonic fields. During the testing of the installation, the results were obtained that are of considerable interest from the point of view of refining the ideas about the mechanism for generating cavitation effects. It was found that preliminary treatment of the liquid in an ultrasonic field with the aim of its degassing for 15–20 min provides a significant increase in the reproducibility of measurements, especially for liquids with a high gas content. Based on a comparison of the time dependences of the signals of the cavitation sensor and the photomultiplier output, the characteristic stages of the development of the cavitation region are distinguished, which differ in the dynamics of the development of the cavitation region and in the composition of the cavitation noise spectra recorded.

All-Optical Formation and Manipulation of Microbubbles on a Porous Gold Nanofilm.

Microbubble generation and manipulation in aqueous environments are techniques that have attracted considerable attention for their microfluidic and biological applications. Ultrasonic and hydrodynamic methods are commonly used to form and manipulate microbubbles, but these methods are limited by the relatively low precision of the microbubble sizes and locations. Here, we report an all-optical method for generation and manipulation of microbubbles with ~100 nm precision by using “hot spots” on a porous gold nanofilm under the illumination of near-infrared focused laser beam. The microbubble diameter ranged from 700 nm to 100 μm, with a standard deviation of 100 nm. The microbubbles were patterned into two-dimensional arrays, with an average location deviation of 90 nm. By moving the laser beam, the microbubbles could be manipulated to a desired region. This work provides a controllable way to form and manipulate microbubbles with ~100 nm precision, which is expected to have applications in optofluidic and plasmonic devices.

Numerical Analysis of Water and Air in Venturi Tube to Produce Micro-Bubbles

Two-phase flow regimes are affected by conduit position, alignment, geometry, flow direction, physical characteristics, and flow rate of each phase as well as the heat flux toward the boundaries. Due to the importance of two-phase flow, numerous regimes have been identified. The first step in studying micro-bubble formation inside a venturi tube is to recognize the type of flow regimes. In this study, which is devoted to the study of micro-bubble formation, a numerical investigation by OpenFOAM software and a VOF model was conducted. Results suggest that flow regime inside the venturi tube is roughly similar to flow regimes inside the horizontal tubes. For having bubble flow and consequently forming micro-bubble, flow rate of gas phase should be very smaller than liquid phase flow rate while the air inlet diameter should be chosen much smaller than water input diameter. Numerical simulations indicate that the best results are achieved for the water velocity of about 1-2m/s.

Continuous formation of microbubbles during partial coalescence of bubbles from a submerged capillary nozzle

AbstractBubble formation from a downward‐pointing capillary nozzle was investigated in this study. The experiments were conducted at gas flow rate of 40–5,400 ml/h and inner nozzle radius of 0.030–0.255 mm. Experimental results show that microbubbles are formed continuously at moderate Weber number, which was not reported in pervious investigations with injecting gas through an upward‐pointing capillary nozzle. High‐speed visualization indicates that the formation of microbubbles arises from the convergence of the capillary waves induced by the partial coalescence of larger bubbles. A bubbling regime map is given to identify the critical conditions for the formation of microbubbles. In the present air‐water experiments, the generated microbubbles are 20–170 μm in diameter. From experimental data, a scaling law for microbubble size is proposed as a function of Weber and Bond numbers.

Study on microbubble of cellulose acetate microfilm of the Republic of China (AD 1912\u20131949) collected in the Second Historical Archives of China

The white spots known as microbubbles that are formed in cellulose acetate film, significantly affects the texture of the image. However, the formation of microbubbles and their corresponding microstructure are poorly understood. In this paper, cellulose acetate microfilm from the Republic of China (AD 1912–1949) collected in the Second Historical Archives of China was chosen as a prototype to investigate the causes of microbubble disease for the first time. A comparative study was conducted between the film samples with and without microbubbles. Herein, the microstructural analyses including optical and SEM microscopy were conducted. The crystals in the microbubbles proved to be triphenyl phosphate as identified by NMR spectroscopy and SEM–EDX. Comparative properties of the film substrate with and without microbubbles were measured by TG, XRD and FT-IR spectroscopy. The results show that formation of microbubbles was generally accompanied with the vinegar syndrome and was produced between the protective and emulsion layers with the different types of shapes along the closed structure (the diameter of ~ 0.1–2 mm). The formed microbubble was filled with plasticizer. Based on the above-mentioned results, the possible formation process of microbubble was proposed in the present study. The results can provide support for the cause of microbubbles and basis for the conservation of photographic films.

Lipiodol visibility under ultrasound.

Lipiodol is an oil-based solution commonly used in hysterosalpingogram (HSG), but not hysterosalpingo contrast sonography (HyCoSy). In women with unexplained infertility, evidence suggests that tubal flushing with Lipiodol results in improved fertility post-procedure. We propose that Lipiodol can be visualised under ultrasound similar to commonly used saline, and hence utilised for HyCoSy, allowing the benefit of an oil-based tubal flushing to occur with HyCoSy. To examine whether Lipiodol is visible sonographically, assess optimal agitated Lipiodol mix and ultrasound settings for visibility, and compare visibility to agitated saline, routinely used for HyCoSy. Two separate sonographers with identical ultrasound machines and model pelvises recorded images with varying degrees of agitated Lipiodol and ultrasound settings, in addition to capturing images with no fluid and agitated saline. Each test was performed in quadruplicate and in random order. Images were read by 47 blinded reporters and visibility reported on a scale of one (not visible) to five (clearly visible). The mean visibility score for images captured where the Lipiodol sample was agitated five times prior to injection to allow the formation of air microbubbles, regardless of ultrasound setting, were higher than or not different from that for agitated saline (all P>0.7 when not different, <0.001 when higher). Sonographic visualisation of agitated Lipiodol is similar or better than that of agitated saline. Lipiodol may therefore present a possibility for use with HyCoSy, with the added benefit of oil-based tubal flushing, avoiding the radiation exposure of HSG and concurrently providing pelvic soft-tissue evaluation.

Micro hole fabrication in TiN-Al2O3 ceramic composite by SiC powder assisted micro- EDM

Considering the importance of ceramics in many microdevice applications, a modified micro-electrodischarge process in which the addition of silicon carbide powders in the dielectric was used to fabricate high aspect ratio microholes in dense and hard TiN-Al2O3 ceramic composite has been described in the present paper. TiN-Al2O3 ceramics has been prepared by reactive hot pressing technique. Response Surface Methodology (RSM) has been employed to design and optimize the experimental input parameters like voltage, capacitance, and tool rotation speed and for evaluating the responses in terms of Material Removal Rate (MRR), Electrode Wear Rate (EWR), Radial Overcut (ROC) and Taper Angle (TA). SiC powder addition has shown the improvement in MRR by 6.5 times, reduction of TA by 2 times and reduction in ROC by 1.5 times. However, EWR has increased by 1.8 times. Improvement in the machining performance has been analysed with respect to the early breakdown of the dielectric fluid by the addition of SiC powder and the enlargement of the discharge gap. Topographies of the machined surfaces analysed from the Scanning Electron Micrographs (SEM) show smoothening of the surface by SiC powder addition and reduction of tool rotation speed. Chemical compositions of the machined surfaces determined by energy dispersive spectral analysis (EDS) showed the formation of amorphous Ti-Al-O-N phase by the discharge. Thermal micro-cracking of the amorphous solidified melt, spalling, micro-bubble formation and accumulation of spherical electrode debris have been observed during the machining of TiN-Al2O3 ceramic-composite.

Isosbestic light absorption by metallic dimers: effect of interparticle electromagnetic coupling.

Isosbestic plasmonic nanostructures, which feature an invariance of optical absorption and heat generation upon varying the incident light polarization, have broad application in many fields such as nanochemistry, optical nanoantennas, and microbubble formation. In this study, we focus on the isosbestic optical absorption by metallic dimers and systematically investigate the coupling between two interacting particles by using both the superposition T-matrix method and dipole approximation model. We observe that the interparticle coupling effects on particle absorption can be both positive and negative, compared to an isolated particle. Meanwhile, the optical absorption properties of spheres with small size parameters can realize more flexible control through changing the sphere size, interparticle distance, and incident light wavelength. For illuminations with incident light propagating perpendicularly to the line joining the centers of the two spheres, isosbestic conditions will be satisfied as long as the absorption efficiencies for transverse and longitudinal illuminations are equal. For transverse illuminations along the dimer axis, the ratio of absorption efficiency of the two metallic spheres presents the fluctuation change with the interparticle distance. Owing to the strong interparticle coupling effects, it even leads to the absorption efficiency of the far sphere being higher than that of the near sphere. Our results are aimed at expanding our understanding of the interparticle electromagnetic coupling effects on isosbestic light absorption in plasmonic nanoparticle systems.

Drop impact on thin powder layers: pattern formation by air entrapment.

Impact of drops on thin powder layers displaces the powder particles radially outward producing shallow craters with thick rims, for example, as observed on dust layers on the floor. Here, we report that the patterns formed on thin powder layers by drop impact are not limited to such crater-like ones. Instead, depending upon the layer properties, disc or disc-plus-ring shaped patterns are formed at the impact point. We show that air entrapment and micro-bubble formation during the drop impact result in the formation of such patterns. Based on high-speed imaging, scaling analyses, and measurements with various liquids and powder layers, we propose a mechanism for the formation of such patterns. The phenomenon that we report can open further investigations on drop impact on the granular matter.

Towards Automatically Controlled Dosing for Selective Laser Trabeculoplasty.

PurposeSelective laser trabeculoplasty (SLT) is a treatment option for open-angle glaucoma; however, it lacks an instant evidence for successful irradiation. So far ophthalmologists use the visible appearance of permanent champagnelike bubbles (macro bubbles) as an indicator for appropriate pulse energy. We hypothesize that micro bubbles, which start energetically far below the appearance of macro bubbles, already trigger the therapeutic benefit. Here we present two methods to capture the onset of these micro bubbles.MethodsThe trabecular meshwork of freshly enucleated porcine eye globes was irradiated with a series of 15 pulses with a pulse duration of 1.7 μs and with increasing energy at a repetition rate of 100 Hz per each spot of 200 μm in diameter. An optical and an optoacoustic method have been developed and appropriate algorithms investigated towards the real-time detection of the onset of micro bubbles.ResultsBoth observation methods are capable of detecting micro bubble nucleation. Threshold radiant exposures were found at 310 ± 137 mJ/cm2. By combination of both methods a sensitivity and specificity of 0.96 was reached.ConclusionsIn case that the therapeutically demanded pressure reduction is already achieved with these micro bubbles, which needs to be proven clinically, then the methods presented here can be used in an automatic feedback loop controlling the laser irradiation. This will unburden the clinicians from any dosing during SLT.Translational RelevanceAutomatic real-time pulse energy dosing based on the formation of micro bubbles in SLT significantly improves and facilitates the treatment for the physician.

Lipid-functionalized porous oxide nanoparticles for acoustic imaging and site-directed therapy

While most US contrast agents are fluid-filled micro- or nanoparticles, their stability of fluid-filled particles is limited by inherent Laplace pressure and equilibrium with the surroundings. Here, I will present our work designing silica nanoparticles of ∼100 nm with specifically tailored surfaces that can nucleate the formation of ultrasound-responsive microbubbles under reduced acoustic pressures. I will discuss the underlying materials science behind their activity, the effects of chemical functionalization on acoustic contrast (with the potential for stimulus-responsiveness), and applications in imaging and directed mechanical cell killing.