Dynamics Of Laser-induced Bubble Research Articles

Secondary cavitation bubble dynamics during laser-induced bubble formation in a small container.

We investigated secondary cavitation bubble dynamics during laser-induced bubble formation in a small container with a partially confined free surface and elastic thin walls. We employed high-speed photography to record the dynamics of sub-mm-sized laser-induced bubbles and small secondary bubble clouds. Simultaneous light scattering and acoustic measurements were used to detect the oscillation times of laser-induced bubbles. We observed that the appearance of secondary bubbles coincides with a prolonged collapse phase and with re-oscillations of the laser-induced bubble. We observed an asymmetric distribution of secondary bubbles with a preference for the upstream side of the focus, an absence of secondary bubbles in the immediate vicinity of the laser focus, and a migration of laser-induced bubble toward secondary bubbles at large pulse energies. We found that secondary bubbles are created through heating of impurities to form initial nanobubble nuclei, which are further expanded by rarefaction waves. The rarefaction waves originate from the vibration of the elastic thin walls, which are excited either directly by laser-induced bubble or by bubble-excited liquid-mass oscillations. The oscillation period of thin walls and liquid-mass were Twall = 116 µs and Tlm ≈ 160 µs, respectively. While the amplitude of the wall vibrations increases monotonically with the size of laser-induced bubbles, the amplitude of liquid-mass oscillation undulates with increasing bubble size. This can be attributed to a phase shift between the laser-induced bubble oscillation and the liquid-mass oscillator. Mutual interactions between the laser-induced bubble and secondary bubbles reveal a fast-changing pressure gradient in the liquid. Our study provides a better understanding of laser-induced bubble dynamics in a partially confined environment, which is of practical importance for microfluidics and intraluminal laser surgery.

The impacts of material acoustic impedance and thickness on single laser-induced bubble dynamics and determining factors in resulting pressure

The objective of this paper is to experimentally identify the primary sources of pressure when a laser-induced cavitation bubble is collapsing to a wall with specific emphases on the material acoustic impedance and thickness. Both high-speed videos and local wall pressure measurements were performed for various standoff ratios γ, bubble diameters, and wall materials. In the case of a rigid wall, in addition to the known high pressure for γ<0.6 where the bubble attaches and collapses on the wall (ring collapse), at γ≈1.12 where the jet is dominant, and low pressure obtained at γ≈0.913, where neither effect is significant, we further captured similar pressure profiles during the collapse after the first rebound at γ≈1.16 for the ring collapse, γ≈1.79 for the jet, and γ≈1.41 for the minimal, respectively. This indicates a strong jet is typically followed by a strong ring collapse. Generally, the pressure from the second collapse increases faster with the bubble size than that of the first collapse. For walls featuring smaller acoustic impedance or thickness, which cannot be approximated as rigid bodies or accessed by pressure sensor, our unique bubble edge analyzing tool shows that the ring collapse and jet effects are moved to smaller values of γ. The maximum pressure exerted on the wall in these cases is smaller than that on the rigid wall. Finally, we summarized the asymptotic evolution curves of each edge which bound the bubble dynamics at different standoff ratios.

Bubble nucleation and jetting inside a millimetric droplet

In this work we present experiments and simulations on the nucleation and successive dynamics of laser-induced bubbles inside liquid droplets in free-fall motion, i.e. a case where the bubbles are subjected to the influence of a free boundary in all directions. Within this spherical millimetric droplet, we have investigated the nucleation of secondary bubbles induced by the rarefaction wave that is produced when the shock wave emitted by the laser-induced plasma reflects at the drop surface. Interestingly, three-dimensional clusters of cavitation bubbles are observed. Their shape is compared with the negative pressure distribution computed with a computational fluid dynamics model and allows us to estimate a cavitation threshold value. In particular, we observed that the focusing of the waves in the vicinity of the free surface can give rise to explosive cavitation events that end up in fast liquid ejections. High-speed recordings of the drop/bubble dynamics are complemented by the velocity and pressure fields simulated for the same initial conditions. The effect of the proximity of a curved free surface on the jetting dynamics of the bubbles was qualitatively assessed by classifying the cavitation events using a non-dimensional stand-off parameter ${\Upsilon\hskip -1,05em -\,}$ that depends on the drop size, the bubble maximum radius and the relative position of the bubble inside the drop. Additionally, we studied the role of the drop's curvature by implementing a structural similarity algorithm to compare cases with bubbles produced near a flat surface to the bubbles inside the drop. Interestingly, this quantitative comparison method indicated the existence of equivalent stand-off distances at which bubbles influenced by different boundaries behave in a very similar way. The oscillation of the laser-induced bubbles promotes the onset of Rayleigh–Taylor and Rayleigh–Plateau instabilities, observed on the drop's surface. This phenomenon was studied by varying the ratio of the maximum radii of the bubble and the drop. The specific mechanisms leading to the destabilisation of the droplet surface were identified.

Investigation of laser-induced bubble dynamics in water at high hydrostatic pressures

Hydrostatic pressure is a key factor that influences laser-induced bubble dynamics in water. In this work, we investigated laser-induced bubble dynamics at high hydrostatic pressures up to 53.2 MPa, by using a high-pressure chamber combined with the shadowgraph imaging technique. It was shown that at the atmosphere pressure, the bubble evolution agrees well with the Keller-Miksis model during the free expansion and collapse phase. As the ambient pressure increases, both the size and the oscillation period of the bubble decreases dramatically as a consequence of faster dynamics. The maximum bubble radius, as well as the collapse time, decrease nonlinearly with the increasing pressure; while the pressurization effect on bubble expansion before 100 ns is negligible due to the high internal bubble pressure in the early stage. Time-resolved plasma emission images were also taken with an ICCD camera to illustrate the plasma evolution at high hydrostatic pressures. It was demonstrated that at a high pressure above 40 MPa, the plasma can gain energy from the bubble collapse, while the bubble will lose its energy, which may lead to a shorter collapse time than that obtained from the numerical calculation. This work provides insight into laser-induced bubble dynamics and the plasma-bubble interaction at high hydrostatic pressures.

Impact of solid particles on cavitation behaviors and laser-induced degradation in aqueous suspension

A method for degrading organic pollutants in suspension by applying laser-induced cavitation is presented. Cavitation bubbles are produced remotely by laser beams, achieving a purpose of non-contact degradation. In this work, laser-induced bubble dynamics in SiO2 sand suspension were studied by high-speed imaging. Pulsating characteristics of cavitaiton bubbles in the infinite domain and near a solid boundary were investigated among various laser energies and sand concentrations. Furthermore, the extent of degradation after processing in suspension and the mechanism were analyzed. Results indicate that solid particles in the liquid medium reduce the extent of degradation. However, the extent of degradation may rebound at a proper sand concentration. In addition, compared to several small bubbles in a bubble string (in the infinite domain), a single larger bubble (near a solid boundary) has a much higher degradation ability.

Dynamics of laser-induced cavitation bubbles near a short hole and laser cavitation processing with particles

The interest in pulsation process of laser-induced cavitation bubble in infinite domain or near a solid boundary has increased greatly in recent years. However, studies on dynamics of laser-induced bubbles near a small hole are few. In this work, dynamics of laser-induced cavitation bubbles before and after going through a small hole was studied by high-speed imaging. Various dimensionless parameter, laser energies, hole diameters and hole lengths were selected to investigate the bubble pulsation. Furthermore, a novel surface treatment method of small hole assisted laser cavitation processing in SiO2 particles suspension was proposed to improve surface quality. The surface morphology, residual stress, and roughness of 1060 aluminium alloy after laser cavitation processing were investigated. Results indicate that dimensionless parameter and hole’s size have a great impact on bubble pulsation. Maximum instantaneous velocity of the front and rear walls of the bubbles is about 47 m/s and 119 m/s respectively when the bubble pulsates behind the hole. The movements of the bubbles may cause the particles to impact the surface, producing small hollows and providing concentrated residual stress.

Measurement of dynamics of laser-induced cavitation around nanoparticle with high-speed digital holographic microscopy

Micro/nano bubble formation on the surface of laser-irradiated nanoparticles has been widely studied in various industrial applications. The elucidation of the mechanism underlying cavitation induced by irradiating nanoparticles with laser is imperative. In this work, high-speed digital holographic microscopy is applied to visualize the in-situ dynamics of laser-induced bubbles generated on nanoparticles randomly dispersed in liquids. The growth and collapse of a bubble along its 3D trajectory are quantified. Experimental results show two patterns of bubble formation. One is that the maximum bubble wall speeds occur during either expansion or contraction. The other is that the maximum speeds are similar in both periods. It is found that the durations of growth and collapse are not equal, and their difference increases with the bubble maximum diameter, which is caused by altered heat transfer processes in bubbles. It implies large bubbles expand relatively quickly and shrink relatively slowly. This work will help understand the interaction among laser, nanoparticles and surrounding medium.

Hybrid analytical/numerical modeling of nanosecond laser-induced micro-jets generated by liquid confining devices

The generation of micro-jets with pulsed laser irradiation is a key enabling technique for microfluidic devices, printers and needle-free drug injectors. Modeling approaches for such devices are essential to optimize their design and performance. Here we present a hybrid analytical/numerical model to simulate nanosecond laser-induced micro-jets generated by a dual-chamber liquid confining device. The simulated device consists of two chambers; the first one is closed and filled with a propellant liquid and the second is filled with the liquid to be ejected and equipped with a nozzle. Laser-induced cavitation is generated in the first chamber, which is separated by an elastic membrane from the second one, to reduce the thermo-mechanical impact of the absorbed laser energy on the liquid to be ejected. By modifying the generalized form of the Rayleigh–Plesset equation to account for the pressure variation inside the chamber, we show that the geometry of the liquid confining device affects drastically laser-induced bubble dynamics and the resulting jet ejection dynamics. We also demonstrate the effect of the membrane size, laser energy and nozzle size variation on the micro-jet dynamics. We found that such devices can generate micro-jets (velocity: 0.93 m/s to 48.39 m/s) suitable for micro-drop printing (volume: 0.097 nL to 7.68 nL). Although we focused on printing applications, the modeling approach presented here can be widely adapted for designing and optimizing needle-free drug injectors and microfluidic devices.

High fidelity visualization of multiscale dynamics of laser-induced bubbles in liquids containing gold nanoparticles

Cavitation in pure liquids and in liquids containing nanoparticles enables applications in mechanics, bio-medicine, and energy. Its evolution carries a significant interest. We describe the multiscale dynamic evolution of ultrafast-laser-induced cavitation in pure and gold-nanoparticles-doped liquids in one-dimensional geometries induced by non-diffractive ultrashort Bessel-Gauss laser beams. Covering the complete electronic and thermomechanical cycle, from the early plasma phase to bubble cavitation and collapse on ms timescales, we reconstitute, using time-resolved imaging with amplitude and phase sensitivity, the hydrodynamic phenomena concurring to bubble evolution. We indicate geometry-specific instabilities accompanying the collapse. The insertion of gold nanoparticles of 200 nm size has subtle effects in the process energetics. Albeit a moderate field enhancement minimizing the contribution to breakdown, the nanoparticles play a role in the overall relaxation dynamics of bubbles. The evolving bubble border in nanoparticles-containing liquids create a snow-plough effect that sweeps the nanoparticles at the gas liquid interface. This indicates that during the macroscopic cavity development, the nanoparticles were removed from the interaction region and dragged by the hydrodynamic movement. We thus shed light on the evolution of cavitation bubbles not triggered but perturbed by the presence of nanoparticles.

Laser-induced bubble dynamics inside and near a gap between a rigid boundary and an elastic membrane

Aspects of laser-induced bubble dynamics in sample geometry closely resembling intraocular environment were studied. Laser pulses with a few millijoules of energy were focused into the sample, producing optical breakdown followed by formation of single bubbles. The sample consisted of a piece of polymethyl methacrylate (PMMA) material and a thin polyethylene (PE) elastic membrane which was carefully positioned parallel to the flat PMMA surface, creating a small and adjustable gap between them. The arrangement was placed in distilled water. Such geometry is frequently encountered in ophthalmology, specifically in posterior capsulotomy where there is a gap present between the intraocular lens and the posterior capsule. The formation and evolution of the laser-induced bubble was recorded with a high speed camera for different positions of the laser focus, i.e. inside the gap as well as outside the gap, in the water. The bubble dynamics was compared to the dynamics of the bubbles created near a rigid boundary alone and near an elastic membrane alone. The comparison showed that the evolution of the bubble created inside the gap can be described as a combination of the features which are characteristic for the rigid boundary and the elastic membrane cases, depending on relative dimensions of the gap and the bubble and on their relative positions. Possible influence on related medical procedures is discussed.

Analysis of thulium fiber laser induced bubble dynamics for ablation of kidney stones.

The Thulium fiber laser (TFL) is being explored as an alternative to the Holmium : YAG laser for lithotripsy. TFL parameters differ in several fundamental ways from Holmium laser, including smaller fiber delivery, more strongly absorbed wavelength, low pulse energy/high pulse rate operation, and more uniform temporal pulse structure. High speed imaging of laser induced bubbles was performed at 105,000 frames per second and 10 μm spatial resolution to determine influence of these laser parameters on bubble formation and needle hydrophone data was also used to measure pressure transients. The TFL was operated at 1908 nm with pulse energies of 5-65mJ, and pulse durations of 200-1000μs, delivered through 105-μm-core and 270-μm-core silica optical fibers. Bubble dynamics using Holmium laser at a wavelength of 2100 nm with pulse energies of 200-1000 mJ and pulse duration of 350 μs was studied, for comparison. A single, 500 μs TFL pulse produced a bubble stream extending 1200 ± 90 μm and 1070 ± 50 μm from fiber tip, with maximum bubble widths averaging 650 ± 20 μm and 870 ± 40μm (n = 4), for 105 μm and 270 μm fibers, respectively. These observations are consistent with previous studies which reported TFL ablation stallout at working distances beyond 1.0 mm. TFL bubble dimensions were four times smaller than for Holmium laser due to lower peak power and smaller fiber diameter used. The maximum pressure transients measured 0.6 bars at 35 mJ pulse energy for TFL and 7.5 bars at 600 mJ pulse energy for Holmium laser. These fundamental studies of bubble dynamics as a function of specific laser and fiber parameters may assist with optimization of the TFL parameters for safe and efficient lithotripsy in the clinic. Image of bubble formation during fiber optic delivery of Thulium fiber laser energy in saline (35 mJ, 500 μs).

Dynamical Studies on Laser Processes Induced by Short Pulse Lasers: From Nanoseconds to Milliseconds

Laser processes induced by short pulse lasers are widely applied in industries and research fields. Details of these processes depend on the laser wavelength and pulse duration of lasers used, materials irradiated, irradiation conditions such like power density and repetition rate and other parameters. To elucidate the details of these processes, we have developed a technique, which is named as high-speed laser stroboscopic videography, to take fast videos to visualize these processes. By combining a newly developed high-speed video cameras and high-repetition rate short pulse lasers, the technique allows us to take videos as fast as 1μs interval in several recording modes, and gives unique information on several laser processes. In this paper we presents some examples of such studies on laser peening, dynamics of laser-induced bubbles in liquids, and micromachining on hard and brittle materials by a femtosecond laser.

Dynamics of laser-induced bubble and nanoparticles generation during ultra-short laser ablation of Pd in liquid

In this work, the dynamics of multiple cavitation bubbles produced by femtosecond laser ablation of a palladium target submerged in acetone is studied by means of time-resolved fast shadowgraphy technique. The data have evidenced the periodic growth and collapse of the bubbles and the consequent emission of material together with the role played by the laser focus position. Comparing the results with the previsions of the Rayleigh–Plesset model a good agreement is found. The nanoparticles obtained under different focusing conditions are characterized by means of TEM analysis. Their dimension and distribution are correlated with the bubbles dynamics.

Experimental investigation of the effect of ambient pressure on laser-induced bubble dynamics

The effect of ambient pressure on the dynamics of laser-induced bubbles was investigated by a fiber-optic diagnostic technique based on probe beam deflection (PBD). The experimental criterion for judging the maximum bubble radius is modified to the average value of the detecting distances at which the characteristic waveform signals appear. The ambient pressure affects the maximum radius and collapse of bubble strongly. The experimental results indicate that the maximum bubble radius and the collapse time both decrease nonlinearly while the ambient pressure increases linearly, and the decreasing velocities of them are smaller at a larger ambient pressure. The predicted value of collapse time has a good agreement with experiment at larger ambient pressure.

The influence of thermodynamic gas parameters on laser-induced bubble dynamics in water

The oscillating properties of laser-induced cavitation bubbles in water are investigated by means of a fiber-optic sensor based on optical beam deflection. The experimental results show two important points. One is that the smaller the bubble radius the more quickly the bubble surface moves. Thus, the variations of the temperature and the pressure inside the bubble will be close to those of an adiabatic process. The other is that the high-energy vapor inside the newborn bubble diffuses and coagulates rapidly through violent expansion and thermal conduction. Thus, the gas content of the bubble reduces significantly in the first oscillation. Numerical simulation is made for the bubble model with consideration of liquid viscosity, surface tension, and gas content. Through modification of the polytropic index and the gas content parameter, two parameters of this model, the numerical results fit the experimental results well.

激光空泡刚性半球面内运动

激光空泡刚性半球面内运动

Experimental investigation of laser-induced bubble dynamics near elastic/soft material in distilled water

This study deals with an experimental investigation of the dynamics of laser-induced single bubble near the rigid material plate and near the elastic/soft material plate in the distilled water at room temperature under atmospheric pressure. A pulsed Nd:YAG laser was focused into the distilled water to make plasma and single bubble. The bubble repeated expanding and shrinking motion several times, and then collapsed. This behavior occurred on the sub-millisecond timescale. The solid wall near the bubble makes an asymmetric flow field. Many experiments on the behavior of laser-induced bubble near the rigid material have been reported. The bubble near the solid wall moves toward the rigid wall during its shrinking and rebounding process. The behavior of laser-induced bubble near the soft material, however, has not been well clarified. The soft material such as body tissue can deform and influence the behavior of the laser-induced bubble. Since the high peak power laser has been applied in the field of bioengineering and medical treatment, it is of great importance to clarify the effect of the soft material near the laser-induced cavitation bubble. In this research the behavior of laser-induced bubble near the elastic/soft material was visualized with schlieren method and investigated.

Single Bubble Behavior Induced by Nd:YAG Laser Focusing Near Solid Wall in Liquid Nitrogen

This paper deals with an experimental investigation and visualization on the dynamics of laser induced single bubble in liquid nitrogen near an aluminum wall in cryostat. The cryogenic liquid nitrogen has the characteristic feature of the low latent heat, surface tension, and viscosity, as compared with the normal temperature water. Cavitation phenomena in cryogenic liquid may be different from the phenomena in water at normal temperature. However, there have been only a few reports on the single bubble dynamics combined with laser beam irradiation in cryogenic liquid. In this experiment the plasma is produced by focusing of Nd:YAG laser beam of second harmonics in liquid nitrogen. Laser induced bubble dynamics and interaction with the solid wall have been studied by flow visualization. This paper also shows the comparison between the dynamics of laser-induced single bubble in liquid nitrogen and in distilled water. We have clarified that the behavior of laser induced bubble in liquid nitrogen is different from that in distilled water at normal temperature.

Self-limited growth of laser-induced vapor bubbles around single microabsorbers

Laser-induced bubble dynamics around micrometer-sized absorbers in water is studied. A single transient microbubble forms around the whole laser-heated particle due to vaporization of the surrounding water. Using 12ns laser pulses, the bubble size increases with radiant exposure, whereas for 240 and 1800ns pulses multiple bubble oscillations with a maximum bubble diameter are observed, which is almost independent from the applied radiant exposure. In this case, thermal decoupling of the expanding bubble from the absorber by the insulating vapor limits the heat transfer from the particle to the bubble. The resulting self-limited bubble growth can increase the precision of cellular laser microsurgery.

Prediction of Holmium-Yttrium-Aluminum-Garnet (Ho: YAG) Laser-Induced Bubble Dynamics in Whole Blood

Prediction of Holmium-Yttrium-Aluminum-Garnet (Ho: YAG) Laser-Induced Bubble Dynamics in Whole Blood