Formation Of Cavitation Bubbles Research Articles

Biofilm removal from Difficult-to-Reach places via secondary cavitation within a constrained geometry mimicking a Periodontal/Peri-Implant pocket

Biofilm removal from the apical region of the periodontal or peri-implant pocket, which is very difficult to achieve with mechanical instruments, is a major unresolved issue in dentistry. Here, we propose the use of photoacoustically induced streaming and secondary cavitation to achieve superior cleaning efficacy in the apical region of the periodontal and peri-implant pocket. We have used a prefabricated narrow wedge system that mimics the consistency of periodontal and peri-implant pockets of both healthy and severely inflamed tissue. We studied the effect of single-pulse modality Er:YAG on Pseudomonas aeruginosa biofilm removal. We used different laser energies, fiber-tip positions, and laser treatment durations. The cleaning process was monitored in real-time with a high-speed camera after each individual laser pulse application. The obtained results suggest that biofilm cleaning efficacy in a difficult-to-reach place in healthy model tissue is directly related to the onset of secondary cavitation bubble formation, which correlates with a significant improvement of biofilm removal from the apical region of the periodontal or peri-implant pocket. In comparison to the healthy tissue model, the laser energy in inflamed tissue model had to be increased to obtain comparable biofilm cleaning efficacy. The advantage of photoacoustic cavitation compared to other methods is that laser-induced cavitation can trigger secondary cavitation at large distances from the point of laser application, which in principle allows biofilm removal at distant locations not reachable with a laser fiber tip or other mechanical instruments.

Investigation of the influence of different liquid temperatures on the dynamics of long-pulse laser-induced cavitation bubbles

Long-Pulse Laser-induced cavitation bubbles have been identified to hold significant applications in various fields, such as industry and medicine. In this study, the dynamics of cavitation bubbles, induced by a 2.94 μm wavelength Er:YAG laser with an energy of 20 ±1 mJ and transmitted via sapphire fiber optics into distilled water at different temperatures, were investigated. The adiabatic expansion theory was utilized to predict the maximum length (Lmax) and the maximum width (Wmax) of the cavitation bubbles at different liquid temperatures. Excellent alignment was observed between the theoretical predictions and the experimental data. Using this theory, the local overheated liquid temperature was deduced to be ∼180 °C during the formation of cavitation bubbles. It was found that as the liquid temperature increased, the collapse position of the cavitation bubbles, relative to the normalized distance (γ) from the fiber end face, decreased. This study reveals the importance of considering the potential risk of damage to fiber optics from the shockwaves and microjet streams generated by cavitation bubbles in high-temperature conditions.

Experimental study on the dynamics of a spark bubble near the top of a cylinder and associated annular secondary cavitation bubbles

This paper presents an experimental study focused on the annular secondary cavitation caused by the interaction between a high-voltage spark bubble and a cylinder. A 2000 V high-voltage underwater electric discharge was used to create the bubble, which reached a maximum diameter of approximately 31 mm. High-speed photography was employed to capture the behavior of the spark bubble and the induced secondary cavitation bubbles. The formation and evolution of the annular secondary cavitation bubbles near the cylinder's edge were captured and analyzed. The study classified the morphology of the annular secondary cavitation bubbles into three different types based on various bubble distances and cylinder diameters. Notably, unique bubble morphologies, such as the terraced bubble shape, were identified, resulting from the coupling between the spark bubble, the annular secondary cavitation bubble, and the cylinder. The interaction between the annular secondary cavitation bubble and the spark bubble, including coalescence, and the resulting effects on bubble shape and period were investigated. The changes of secondary cavitation bubbles are compared when the cylinder has different chamfer angles. Moreover, the study examined the dynamic characteristics of the bubbles, including their shape evolution, jetting behavior, period length, and pressure pulses upon collapse, at various distances from the top-surface of cylinders with different diameters. The experiment also introduced flow visualization with dye into spark bubble experiments for the first time to trace the vortex around the annular secondary bubble. Additionally, the transparency of bubbles in the images was improved through multi-source lighting techniques.

The improvement of freezing time and functional quality of frozen mushrooms by application of probe-type power ultrasound

The study proposes a novel ultrasound-assisted freezing method for button mushrooms, which combines probe-type ultrasonication and immersion freezing. The effects of power ultrasound in both continuous and pulse modes (at five levels of 50, 100, 200, 300, and 400 W) on the freezing process and quality attributes of frozen mushrooms were investigated. Results showed that ultrasound-assisted freezing significantly reduced freezing time compared to immersion freezing, potentially due to the formation of abundant cavitation bubbles that enhanced heat and mass transfer rates. The lowest weight loss was achieved by the continuous mode of 200 W ultrasound (UC200), which may be attributed to the formation of smaller ice crystals during ultrasonication. Ultrasound also prevented acidification and resulted in the retention of the samples' pH and higher total solid solution than immersion freezing. The optimal ultrasound power and duty cycle for different freezing outcomes were determined using the TOPSIS method. UC200 was found to be the best treatment for total freezing time and minimizing weight loss, while a combination of UC200 and UC400 was optimal for gumminess and chewiness. The proposed ultrasound-assisted freezing method shows promise as an environmentally friendly and safe technique for commercial use in the future.

Laser-activated irrigation: Cavitation and streaming effects from dental lasers

IntroductionThe aim of the present study was to assess the generation of laser-activated irrigation (LAI) with a 9,300-nm CO2 laser, a 455- and 970-nm diode laser, as well as an 810- and 980-nm diode laser with and without carbon-coated “hot tips” for improved irrigation in endodontics. Therefore, the formation of cavitation bubbles at the laser tip ends in different liquids was evaluated and compared with the traditionally applied Er:YAG laser.MethodsThe CO2 laser was applied at different power settings at a repetition rate of 14 Hz, SIROLASE for each wavelength at 10% Duty Cycle, and WISER with both wavelengths at different power settings and wavelengths. The LAI was videotaped with a high-speed camera. To measure the streaming velocity due to cavitation, all lasers were loosely coated with carbon particles and activated in pure water. Then, due to LAI, moving particles were videotaped with the same high-speed camera setup. To determine the streaming velocities, the movement of one carbon particle was tracked with the help of a measuring tool in ImageJP software and streaming velocities were calculated.ResultsWith both diode laser devices at four wavelengths, it was only possible to introduce clear cavitation bubbles with low-power parameters (180 mW for the SIROLASE and 200 mW average power for the WISER laser), with the black coating of the laser tips. The 9,300-nm CO2 laser produced clear cavitation bubbles with all tested parameters. Consequently, all tested lasers produced streaming of the liquid, with decreasing velocities at increasing distances from the laser tip: Er:YAG laser 6.4 m/s, CO2 laser up to 5 m/s, and diode lasers in the range of 0.01–0.09 m/s. LIA with the Er:YAG and 9,300-nm CO2 lasers generated high and similar streaming velocities. The diode lasers tested generated significantly lower streaming velocities.

Unintentional formation of nitrate and nitrite ions during nanodiamonds sonication: A source of radical and electron scavengers

Ever since studies on diamond nanoparticles (NDs) expanded, their exceptional colloidal stability was investigated as it is a key parameter for their further use in many applications. While a sonication step is required to deaggregate NDs and obtain stable aqueous suspensions, few works focused on the impact of the sonication process on the suspension composition. High-powered sonication induces the formation of a variety of species by radical pathways including nitrite and nitrate ions, which may act as radical or electron scavengers. Such effect may significantly affect the expected photocatalytic or radiolytic properties of NDs. This work aims to warn about the formation of these ionic species during the deagglomeration of NDs by sonication. Our investigation reveals for the first time that for oxidized detonation NDs, such treatment promotes the formation of additional NO2- ions and hydroxyl radicals, suggesting an increase in cavitation bubbles formation. Hydrogenated particles on the opposite present no overproduction of nitrite ions. Our results also show that these species can be avoided in suspension by sonicating under controlled atmosphere with no significant perturbation of NDs colloidal stability or surface chemistry.

Femtosecond Laser Microsurgery of Mouse Oocytes: Formation and Dynamics of Cavitation Bubbles Under the Action of Sharply Focused Laser Radiation on Various Oocyte Zones

Femtosecond Laser Microsurgery of Mouse Oocytes: Formation and Dynamics of Cavitation Bubbles Under the Action of Sharply Focused Laser Radiation on Various Oocyte Zones

Modeling acoustic emissions and shock formation of cavitation bubbles

Despite significant progress in understanding and foretelling pressure-driven bubble dynamics, models that faithfully predict the emitted acoustic waves and the associated shock formation of oscillating or collapsing bubbles have received comparably little attention. We propose a numerical framework using a Lagrangian wave tracking approach to model the acoustic emissions of pressure-driven bubbles based on the Kirkwood–Bethe hypothesis and under the assumption of spherical symmetry. This modeling approach is agnostic to the equation of the state of the liquid and enables the accurate prediction of pressure and velocity in the vicinity of pressure-driven bubbles, including the formation and attenuation of shock fronts. We validate and test this new numerical framework by comparison with solutions of the full Navier–Stokes equations and by considering a laser-induced cavitation bubble as well as pressure-driven microbubbles in excitation regimes relevant to sonoluminescence and medical ultrasound, including different equations of state for the liquid. A detailed analysis of the bubble-induced flow field as a function of the radial coordinate r demonstrates that the flow velocity u is dominated by acoustic contributions during a strong bubble collapse and, hence, decays predominantly with u∝r−1, contrary to the frequently postulated decay with u∝r−2 in an incompressible fluid.

Investigation of Hydraulic Conditions and Shape of Flip Bucket Spillways on Cavitation Phenomenon by Considering Dynamic Pressures

Abstract Cavitation is one of the destructive phenomena which occurs in hydraulic structures and can cause considerable damage to them. This phenomenon is likely to take place in parts of hydraulic structures where the flow velocity is high and water pressure is below the water vapor pressure, thereby leading to the formation of cavitation bubbles. Dynamic pressures may, frequently and in short time periods, reduce flow pressure to below the vapor pressure of water and form cavitation bubbles as a result. Taking dynamic pressures into account, this study examines the potential for the occurrence of cavitation in flip bucket spillways. This research is based on experimental studies and it focuses on the cavitation phenomenon by measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. Measurements of dynamic and statics pressures on three different models of flip buckets were made within a range of different Froude numbers. Using statistical analyses on pressure fluctuations, this study has obtained the equivalent pressures of the 0.1% incidence probability, which, in turn, have been used, along with static pressures, for calculating the cavitation. Results show that as the Froude number increases (from nearly five to almost ten), the cavitation index decreases, and after that, the trend of cavitation index is reversed and starts to rise. Also, it is demonstrated that the cavitation probability on inlet and outlet scope of the flip bucket is higher than the middle part. Hence, cavitation incidence probability increases while the ratio of width to radius of the bucket rises.

Modeling and Simulation of Hybrid Polymeric Elastic Adhesive Interface for Transducers

AbstractUltrasounds are oscillations in the field of 18 KHz… .100 KHz, which has proven its applicability through many applications starting from the industrial field (ultrasonic defectoscopy, ultrasonic cleaning, etc.) pass through the field of consumer goods (ultrasonic motors, systems operating cameras, high‐precision microscopes, etc.) and reach the medical field such as ultrasound investigations, extremely used today. One of the less known and very new applications at present, but which is trying to make a very important contribution in the field of ecotechnology is the filtration of air by ultrasonic cavitation. In order to achieve air filtration using the phenomenon of ultrasonic cavitation, the ultrasonic system consisting mainly of the ultrasonic transducer must be optimally attached to the lower part of the tank where the air filtration process takes place. In this sense, by modeling and simulation by the finite element method, the thickness of the adhesive layer is determined so that the phenomenon of ultrasonic cavitation to occur efficiently and for a long operating time. Considering the phenomenon of ultrasonic cavitation, the presented research proposes a new method of industrial air filtration in which impurities and inhomogeneities of impure air are germs for the formation of cavitation bubbles so that this phenomenon will lead to their elimination resulting in a higher quality filtered air. The phenomenon of ultrasonic cavitation occurs due to a system of piezoceramic transducers mounted on the bottom of tank. One of the very important problems during the experiments is the fixation of the piezoceramic transducer system on the bottom surface of the tank. This is done with the help of a silicone adhesive that must allow an optimal transfer of the ultrasonic oscillations from the ultrasonic transducer. Thus, determining the thickness of the silicone adhesive layer becomes very important and this is done by performing a modal analysis using the finite element method.

Comparative study of pulsed laser-induced breakdown at a metal-liquid interface at two liquid temperatures using a beam-deflection probe

A pulsed Nd: YAG laser is tightly focussed on a nickel wire-shaped target immersed in a glass cell filled with distilled de-ionized water. The resultant shock wave and cavitation bubble dynamics, occurring because of the laser-induced plasma expansion, are recorded using a pump-probe set-up. The shock wave and cavitation bubble dynamics are recorded at two temperatures of the liquid. It was observed that a higher liquid temperature results in a higher velocity of shock wave propagation, which consequently led to a higher pressure exerted by the shock wave. The experimentally determined shock wave velocities were 1.8 and 1.9 km/s for cold and hot water, respectively. Consequently, the pressure values amounted to 0.23 and 0.27 GPa, respectively. Cavitation bubble radii determined experimentally were 975 μm and 742 μm, for cold and hot water, respectively. Also, a higher liquid temperature led to a higher order of cavitation bubble formation.

Vascularization of Cell-Laden Microfibres by Femtosecond Laser Processing.

To face the increasing demand for organ transplantation, currently the development of tissue engineering appears as the best opportunity to effectively regenerate functional tissues and organs. However, these approaches still face the lack of an efficient method to produce an efficient vascularization system. To answer these issues, the formation of an intra-volume channel within a three-dimensional, scaffold free, mature, and cell-covered collagen microfibre is here investigated through laser-induced cavitation. An intra-volume channel was formed upon irradiation with a near-infrared, femtosecond laser beam, focused with a high numerical aperture lens. The laser beam directly crossed the surface of a dense and living-cell bilayer and was focused behind the bilayer to induce channel formation in the hydrogel core while preserving the cell bilayer. Channel formation was assessed through confocal microscopy. Channel generation inside the hydrogel core was enhanced by the formation of voluminous cavitation bubbles with a lifetime longer than 30 s, which also improved intra-volume channel durability. Twenty-four hours after laser processing, cellular viability dropped due to a lack of sufficient hydration for processing longer than 10 min. However, the processing automation could drastically reduce the cellular mortality, this way enabling the formation of hollowed microfibres with a high density of living-cell outer bilayer.

The use of real-time passive cavitation imaging for monitoring boiling histotripsy treatments

Boiling histotripsy (BH) is a high intensity focused ultrasound method that induces mechanical tissue liquefaction and relies on the formation of a mm-sized vapor bubble at the focus. One challenge of transcutaneous BH is to confirm the presence of such bubble and to differentiate it from prefocal cavitation. Strong prefocal cavitation can shield the focus, prevent initiation of boiling, and lead to unsuccessful treatment, although an echogenic region would still be present on B-mode ultrasound images. Here, a methodology for real-time monitoring of different bubble activity during BH treatment is proposed. Custom BH systems of 1 and 1.5 MHz with inline ultrasound imaging probes connected to a Verasonics V1 system were used for BH treatments in pigs in vivo and in ex vivo tissues. Backscattered signals arriving to the imaging probe were recorded during the 10 ms BH pulses delivered at 1 Hz and passive cavitation imaging (PCI) reconstruction was performed and displayed on top of the B-mode images to identify and classify the regions of bubble activity. Spectral analysis of the PCI signals promoting prefocal cavitation and lack thereof was performed to identify the spectral features corresponding to prefocal cavitation and vapor bubble formation. [Work supported by NIH R01EB007643, R01GM122859, and R01EB25187.]

Probing the cavitation bubbles produced during laser ablation of copper immersed in liquid under tightly focused conditions using shadowgraphy technique

Pulsed laser ablation in liquid (PLAL) has emerged as an efficient method for production of nanoparticles (NPs), especially noble metal NPs. The main advantage of synthesizing NPs by this method is that bare as well as functionalized NPs can be synthesized with great ease. Noble metal NPs have proven to be extremely useful in the fields of biomedicine, sensing technology, energy storage, etc. The properties of such NPs strongly depend on the transient dynamics that occur on the target surface. Hence, in order to control the properties of the NPs and increase their productivity, it is crucial to study the dynamics associated with the technique. Keeping this in mind, a study has been conducted to understand the effect of tight focusing of the pulsed laser beam on the cavitation bubbles generated during PLAL performed on copper (Cu) target using shadowgraphy technique. The results reveal novel dynamics of the formation of cavitation bubbles due to the breakdown of the liquid in addition to the bubble attached to the target. The analysis of such bubbles is carried out and its evolution is studied.

СОНОЛЮМИНЕСЦЕНТНАЯ СПЕКТРОСКОПИЯ КОЛЛОИДНЫХ СУСПЕНЗИЙ: МОЛЕКУЛЯРНАЯ, ИОННАЯ И АТОМАРНАЯ ЛЮМИНЕСЦЕНЦИЯ ПРИ СОНОХИМИЧЕСКОМ РАЗЛОЖЕНИИ НАНОЧАСТИЦ ДИОКСИДА КРЕМНИЯ, СОДЕРЖАЩИХ СОЕДИНЕНИЯ РУТЕНИЯ И МЕДИ

The article is devoted to an example of the sonoluminescence spectroscopy use, which was previously known as a method for analyzing substances from the characteristic spectra of their sonoluminescence only in true solutions, for carrying out a similar analysis of substances contained in insoluble nanoparticles in colloidal suspensions. The solutions sonolysis, that is, their irradiation with ultrasound, is accompanied by the formation of cavitation bubbles that vibrate radially at the frequency of the ultrasonic field. Volatile components of the solution enter the bubbles, evaporating from the liquid-gas interface; nonvolatile components can penetrate into the bubble as a result of the injection of solution nanodroplets into the gas phase, which occurs during intense bubble movements accompanied by their deformation. In a nonequilibrium plasma periodically forming in cavitation bubbles, destruction occurs, as well as collisional excitation of these components, followed by luminescence. It has been shown that this mechanism of sonoluminescence also operates in colloidal suspensions, where substances are present in the form of nanoparticles with sizes less than 50 nm. Such nanoparticles penetrate into moving cavitation bubbles, without destroying them, as part of nanodroplets, and then undergo decomposition in bubble plasma with the excited particles generation as emitters of characteristic sonoluminescence. In this work, we synthesized colloidal suspensions in dodecane of porous SiO2 nanoparticles containing adsorbed Ru(bpy)3Cl2 and CuSO4 salts. During moving single-bubble sonolysis for these suspensions, characteristic emission spectra of Ru and Cu atoms, SiO molecules, and Ru(bpy)3 ions suitable for sonoluminescence spectroscopic analysis were recorded. By comparing the experimental and calculated (at different temperatures) luminescence spectra of Ru atoms, we estimated the electron temperature attained upon acoustic compression of single bubble in colloidal suspension in dodecane: Te = 7000 K.

Astigmatism and spherical aberrations as main causes for degradation of ultrafast laser-induced cavitation in water

The generation of cavitation bubbles in water by focused laser pulses has been thoroughly studied, particularly due to the wide range of applications in biomedical fields, in particular for ophthalmic laser surgery. The presence of optical aberrations in any optical system deteriorates the precision of light focusing and may reduce the laser interaction efficiency in transparent media. In this paper, we analyze the influence of several controlled optical geometrical aberrations in the formation and dynamics of cavitation bubbles in water caused by laser-induced optical breakdown using femtosecond laser pulses. The maximum cavitation bubble diameter reduces with increasing aberrations, showing a drop of the energy coupling efficiency, ultimately leading to the absence of cavitation bubble. The study reveals that the secondary astigmatism and spherical aberrations degrade more rapidly the beam concentration than the other aberrations studied here (namely astigmatism first and second, coma, spherical and trefoil). The cavitation energy threshold becomes equally increased. This observation relates very well to numerical simulations evaluating the laser fluence at and around the focusing plane in the presence of aberrations. These results open the door to more controlled ultrafast laser assisted surgeries and processing in transparent media.

Burst wave lithotripsy – the new evolution stage of extracorporeal shock-wave lithotripsy

Urolithiasis is currently one of the most urgent problems in the world. Every eleventh worldwide inhabitant suffers from this disease. Previously, the only way to get rid of kidney stones and the urinary tract was open surgery, which was characterized by high trauma. Over the past decades, the development of technologies has made a significant contribution to the development of new methods of urolithiasis treatment. One of these methods is extracorporeal shock wave lithotripsy (ESWL). The first lithotripter Dornier HM-1 was produced in 1980. Subsequent models have got many changes, both in terms of ergonomics and power. The researchers noticed that the efficiency of stone crushing in the Dornier HM-1 lithotripter was higher than in newer models since the lower power provided the less intensive formation of cavitation bubbles that prevent the effective transit of subsequent waves through the stone. Nowadays, a new method of remote stone crushing is being developed based on low-amplitude high-frequency technology combined with ultrasonic propulsion, which is the main difference from traditional shock-wave lithotripters. The new technology of stone crushing is called «burst wave lithotripsy» (BWL). Currently, the data have been obtained that this method is more effective in terms of crushing quality and less traumatic.

A Model for Sonochemistry in a Thin Layer Sonochemical Cell: What Constructive Interference Yields

Traditional sonochemistry (TS) in bulk solution is violent and expensive. Typically, a high power (> 60 W) ultrasonic horn is directed at a planar working electrode. Compression and rarefaction oscillations elicit cavitation bubble formation. Upon bubble collapse, high temperature (> 5000 K) and pressure (> 1000 atm) are produced locally, which enhances rates of chemical reactions. Bubble collapse near the electrode causes solvent jets directed at the surface to effect the surface cleaning and mass transport enhancements attributed to TS.While productive, TS obscures quantitative measurement of electron transfer kinetics and mass transport and requires a large laboratory footprint. An alternative and efficient sonochemistry is needed. Thin Layer Sonochemistry (TLS) exploits natural acoustics in a thin layer electrochemical cell. Low power transducers (e.g., quartz crystal oscillators) are appropriate because TLS achieves resonance in the cell to amplify input sound to the limit set by the solvent. TLS is more efficient and allows finer control of experimental and acoustic parameters. The footprint of TLS is minimal, and so TLS is appropriate for energy production applications (e.g., fuel cells) in portable devices.Experience suggests a subtle relationship between acoustic parameters and resonance. Here, a model is presented for calculation and explanation of resonance in a thin layer sonochemical cell. Background physics are explained and a step-by-step assembly guide is presented.

How the Physicochemical Properties of the Bulk Material Affect the Ablation Crater Profile, Mass Balance, and Bubble Dynamics During Single-Pulse, Nanosecond Laser Ablation in Water.

Understanding the key steps that drive the laser‐based synthesis of colloids is a prerequisite for learning how to optimize the ablation process in terms of nanoparticle output and functional design of the nanomaterials. Even though many studies focus on cavitation bubble formation using single‐pulse ablation conditions, the ablation efficiency and nanoparticle properties are typically investigated under prolonged ablation conditions with repetition rate lasers. Linking single‐pulse and multiple‐pulse ablation is difficult due to limitations induced by gas formation cross‐effects, which occur on longer timescales and depend on the target materials’ oxidation‐sensitivity. Therefore, this study investigates the ablation and cavitation bubble dynamics under nanosecond, single laser pulse conditions for six different bulk materials (Au, Ag, Cu, Fe, Ti, and Al). Also, the effective threshold fluences, ablation volumes, and penetration depths are quantified for these materials. The thermal and chemical properties of the corresponding bulk materials not only favor the formation of larger spot sizes but also lead to the highest molar ablation efficiencies for low melting materials such as aluminum. Furthermore, the concept of the cavitation bubble growth linked with the oxidation sensitivity of the ablated material is discussed. With this, evidence is provided that intensive chemical reactions occurring during the very early timescale of ablation are significantly enhanced by the bubble collapse.

Cavitation causes brain injury

In this study, an artificial transparent head surrogate with high-speed photography discovers the formation and collapse of cavitation bubbles near the contrecoup regions as the head is exposed to a sudden translational impact. The cavitation damages the brain surface and produces a shock wave through the brain matter. Based on a novel experimental design, this new finding uncovers the mystery of the motion and deformation of the soft brain matter, which is not visible otherwise. It suggests that current brain injury criteria may underestimate the risk of head collision.