The authors would like to acknowledge the French ANR (grant ANR-10-BLAN-0810 NEQSON) and CEA/DEN/Marcoule.

1. Measurement&#160;of Uranium Sonoluminescence
The thermostated cylindrical sonoreactor is mounted on top of a high-frequency transducer providing 203 or 607 kHz ultrasound. Ultrasonic irradiation with low frequency ultrasound of 20 kHz is performed with a 1-cm2 titanium horn placed reproducibly on top of the reactor. The emission spectra are recorded in the range 230&#8211;800 nm using a spectrometer coupled to a liquid-nitrogen cooled CCD camera. Hydrogen in the outlet gas is measured simultaneously with the spectroscopic study using a quadrupole mass spectrometer (MS).
<ol>
	<li>Prepare the sonoreactor by tightly attaching the glass part onto the high-frequency transducer and the Teflon lid holding the 20 kHz horn onto the glass part. Put the sonoreactor on the translation stage and adjust its position so as to image with the two mirrors the center of the reactor onto the entrance slit of the emission spectrometer.</li>
	<li>Prepare uranyl solutions in perchloric acid by dissolving weighted UO3 samples, provided by CETAMA/CEA France, in a minimal volume of concentrated HClO4 under heating. Adjust then the volume of solution with diluted HClO4. To prepare uranyl solutions in H3PO4 dissolve UO3 samples in concentrated HClO4, evaporate the obtained solution to the wet salts and dissolve the latter in the desired volume of 0.5 M H3PO4.</li>
	<li>Put the solution to study into the sonoreactor. Tightly replace the 20 kHz horn. Add thermocouple and inlet gas tube onto the sonoreactor and connect the outlet gas tube to the entrance of the mass spectrometer.</li>
	<li>Put on the cryostat at ~0-1 &#176;C. Let argon bubble in the solution at a flow rate of 100 ml/min for at least 30 min and start following Ar and H2 MS signals.</li>
	<li>When MS signals are constant, switch on the ultrasonic generator (either the high-frequency one, at 60-80 W, or the 20 kHz one, at 35 W) and wait approximately 20 min until a steady-state temperature of about 10 &#176;C is reached inside the sonoreactor. The H2 MS signal should increase, indicating cavitation and water sonolysis.</li>
	<li>Close the light-tight box around the sonoreactor and start measuring sonoluminescence spectra, each during 300 sec to ensure good signal intensity. For each wavelength interval make three spectra to increase the signal to noise ratio and put second-order-light filter when necessary.</li>
	<li>After measuring the SL spectra, switch off the ultrasonic generator and keep measuring MS signals until a nice baseline is reached. At the same time, measure emission spectra in the absence of US that will allow to correct SL spectra for parasite light.</li>
</ol>
2. Sonochemical Reduction of Pt(IV) in Aqueous Solutions
<ol>
	<li>Prepare a 5 g/L&#160;Pt(IV) solution starting from H2PtCl6&#183;6H2O salt. Remarks: platinum salts are light and moisture sensitive. Keep the remaining salt under inert atmosphere and if possible, carry out the weighting procedure within a nonreactive gas atmosphere glove box.</li>
	<li>Under a fume hood, set up a 50 ml airtight glass reactor equipped with a double jacket (Figure 6).
	 <img alt="Figure 6" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig6highres.jpg" width="500" /> 
	Figure 6: Experimental set-up for Pt(IV) sonochemical reduction at 20 kHz. 1. Ultrasonic generator of 20 kHz ultrasound with 750 W of maximal electric power, 2. Piezoceramic transducer, 3. Titanium horn, 4. Thermostated reactor, 5. Gas inlet, 6. Sample outlet, 7. Thermocouple, 8. PTFE ring.</li>
	<li>Equip the reactor with a Pt-100 thermocouple, a septum, a PTFE gas inlet and also a gas outlet with flow meters calibrated within the range of 100 ml/min. Connect the gas outlet to a water trap (molecular sieves) and finally to a gas mass spectrometer. CAUTION: Be sure to evacuate the gas within the fume hood since CO is a very harmful compound. A CO gas detector in the laboratory is mandatory.</li>
	<li>At the top of the reactor, fix a 1 cm&#178; titanium probe with a piezoelectric transducer supplied by a 20 kHz generator. Ensure that the sonotrode tip is at around 2 cm from the bottom of the reactor.</li>
	<li>Prior to experiments, start the chiller and set the temperature to -18 &#176;C. In the meantime, introduce 50 ml of deionized water within the reactor and make the Ar/CO (10%) gas bubbling deep within the solution with a flow rate around 100 ml/min. Ensure that there is no major leakage by checking the gas outlet flow rate. Be sure that the sonotrode tip is 1 to 2 centimeters below the surface of the liquid and start the gaseous products monitoring.</li>
	<li>After 10 to 15 min, fix the gas inlet slightly below the liquid surface and once the chiller reaches the setup temperature, start the ultrasonic irradiation with an acoustic power of 17 W/ml.</li>
	<li>After 15 to 20 min of ultrasonic irradiation, check that the temperature reaches a steady state around 40 &#176;C. If not, change the chiller settings to meet this requirement.</li>
	<li>Take a precise amount of the H2PtCl6 solution with the help of a syringe equipped with a stainless steel needle. Carefully introduce the needle through the septum and inject the solution within the cavitation zone below the sonotrode tip. Wash out the syringe by gently pumping the solution in and out and finally take a 1 ml sample. Repeat the sampling procedure at regular time intervals of 15 to 30 min.</li>
	<li>Measure the total concentration evolution of Pt ions in solution by ICP-OES analysis after dilution of the aliquots in 0.3 M HNO3. In the meantime, determine the amount of Pt(IV) ions within the system by following the 260 nm band in UV/Vis spectroscopy.</li>
	<li>As soon as no platinum ions can be detected in solution, switch off the ultrasonic irradiation, turn off the gas bubbling and the chiller. Take the platinum nanoparticle suspension out of the reactor.</li>
	<li>Prior to TEM analysis, try to centrifuge the suspension at high rotation speed (20,414 x g) for at least 20 min. Carefully remove the supernatant and store the deposit after drying at room temperature under vacuum or leave it within a small amount of water.</li>
	<li>Some samples can be very difficult to concentrate and can need longer centrifugation time. If it is not successful, use this procedure only to separate the platinum nanoparticles from the bigger titanium particles released in solution during the ultrasonic irradiation and then keep the supernatant this time.</li>
	<li>Disperse one drop of supernatant or few milligrams of dried products in absolute ethanol or isopropanol. Deposit one drop of the suspension on a carbon coated copper grid and proceed to the HRTEM analysis after total evaporation of the solvent.</li>
</ol>
3. Sonochemical Synthesis of Plutonium Colloids
In Marcoule, the ATALANTE facility is equipped with several hot labs and shielded cell lines dedicated to the research and development for nuclear fuel cycle. One of the glove boxes is devoted to the study of the sonochemical reactions of actinides.
<ol>
	<li>Suspend 200 mg of PuO2 (SBET = 13.3 m2/g) in 50 ml of pure water in the sonochemical reactor located in the glove box.</li>
	<li>Equip the reactor with the tight Teflon ring and the 20 kHz ultrasonic probe. Before each experiment, screw a new tip to ensure maximal effect of cavitation and avoid the accumulation of titanium particles in solution resulting from the tip erosion.</li>
	<li>Set the temperature of the cryostat (Huber CC1) situated outside the glove box low enough to manage the temperature increase in solution after the ultrasound will be switched-on. Note that the cooling system is equipped with a heat exchanger to avoid radioactive contamination outside the barrier. Insert the tight thermocouple into the cell to control the temperature of the solution.</li>
	<li>Allow bubbling the solution with pure argon 20 min before sonication (100 ml/min). Note that the Ar bubbling will be applied during the whole sonication experiments to ensure the maximal effects of acoustic cavitation.</li>
	<li>Set the ultrasonic generator to the appropriate amplitude (~30%) in order to obtain the required acoustic power Pac (17 W/cm2) delivered to the solution. Note that the acoustic power is previously measured using the thermal probe method 22. Using the appropriate conditions, the accumulation of hydrogen peroxide in solution (resulting from the combination of hydroxyl radicals induced by the homolytic dissociation of sonicated water molecules) is previously measured in pure water to calibrate the system and allow the reproducibility of the experiment.</li>
	<li>Switch-on the ultrasonic generator and sonicate the PuO2 solution. Adjust the cryostat settings to obtain a temperature of 30 &#176;C in the solution.</li>
	<li>Once the colloids are formed (after 5-12 hr of irradiation), switch-off the ultrasonic generator, transfer the solution to centrifugation tube, and centrifuge during 10 min (22,000 x g) in order to remove the solid phase.</li>
	<li>UV-Vis spectrometer can thereafter be used for direct analysis and characterization of Pu colloids. During sonication, the kinetics of H2O2 accumulation in solution under ultrasound irradiation can also be measured by the colorimetric method at 410 nm (&#949; = 780 cm-1M-1) after diluting 500 &#181;l of sampled solution with 500 &#181;l TiOSO4 (2 x 10-2 M in 2 M HNO3 &#8211; 0.01 M [N2H5][NO3]) followed by centrifugation.</li>
</ol>

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The authors have nothing to disclose.

The most critical parameters for successful observation of sonoluminescence and sonochemistry are: 1) rigorous control of the saturating gas and the bulk temperature during sonication, 2) careful selection of ultrasonic frequency, 3) using an optimal composition of sonicated solution to prevent quenching.
The kinetics of the sonochemical reactions as well as the intensity of sonoluminescence is very sensitive to the temperature of solution submitted to ultrasound: in contrast to the kinetics o...

The use of power ultrasound in numerous industrial and research areas, such as the cleaning of solid surfaces, degassing of liquids, material sciences, environmental remediation, and medicine, has received much attention during the last decade 1. The ultrasonic treatment increases the conversion, improves the yield, and initiates the reactions in homogeneous solutions as well as in heterogeneous systems. It is generally accepted that the physical and chemical effects of ultrasonic vibrations in liquids arise from acoustic cavitation or, in other words, to the implosive collapse of microbubbles in fluids irradiated with power ultrasound 2. Violent implosion of the cavitation bubble generates transient extreme conditions in the gas phase of the bubble, which are responsible for the formation of chemically active species and sonoluminescence. Nevertheless, debate still continues over the origin of such extreme conditions. Spectroscopic analysis of the sonoluminescence helps to better understand the processes occurring during the bubble collapse. In water, saturated with noble gases, the sonoluminescence spectra are composed from OH(A2&#931;+-X2&#928;i), OH(C2S+-A2S+) bands and a broad continuum ranging from UV to NIR part of the emission spectra 3. Spectroscopic analysis of OH(A2&#931;+-X2&#928;i) emission bands revealed formation of nonequilibrium plasma during sonolysis of water 4, 5. At low ultrasonic frequency, weakly excited plasma with Brau vibrational distribution is formed. By contrast, at high-frequency ultrasound, the plasma inside collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. The vibronic temperatures (Tv, Te) increase with ultrasonic frequency indicating more drastic intrabubble conditions at high-frequency ultrasound.
In principal, each cavitation bubble can be considered as a plasma chemical microreactor providing highly energetic processes at almost room temperature of the bulk solution. The photons and the "hot" particles produced inside the bubble enable to excite the non-volatile species in solutions thus increasing their chemical reactivity. For example, the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions is influenced by uranium concentration: photons absorption/re-emission in diluted solutions, and excitation via collisions with "hot" particles contributes at higher uranyl concentration 6. Chemical species produced by cavitation bubbles can be used for the synthesis of metallic nanoparticles without any templates or capping agents. In pure water sparged with argon, the sonochemical reduction of Pt(IV) occurs by hydrogen issued from sonochemical water molecules splitting yielding monodispersed nanoparticles of metallic platinum 7. Sonochemical reduction is accelerated manifold in the presence of formic acid or Ar/CO gas mixture.
Many previous studies have shown the advantages of ultrasound to activate the surface of divided solids due to the mechanical effects in addition to chemical activation 8,9. Small solid particles that are much less in size than the cavitation bubbles do not perturb the symmetry of collapse. However, when a cavitation event occurs near big aggregates or near extended surface the bubble implodes asymmetrically, forming a supersonic microjet leading to the cluster disaggregating and to the solid surface erosion. Ultrasonic treatment of plutonium dioxide in pure water sparged with argon causes formation of stable nanocolloids of plutonium(IV) due to both physical and chemical effects 10.

<table><tbody><tr><td>20 kHz Ultrasound Generator</td><td>Sonics Vibracell</td><td></td><td></td></tr><tr><td>Multifrequency Generator AG 1006</td><td>T&amp;amp;C Power Conversion</td><td></td><td></td></tr><tr><td>Cryostat RE210&amp;nbsp;</td><td>Lauda</td><td></td><td></td></tr><tr><td>Spectrometer SP 2356i</td><td>Roper Scientific</td><td></td><td></td></tr><tr><td>CCD camera SPEC10-100BR cooled with liquid nitrogen</td><td>Roper Scientific</td><td></td><td></td></tr><tr><td>Quadrupole mass-spectrometer PROLAB 300</td><td>Thermoscientific</td><td></td><td></td></tr><tr><td>Centrifuge Sigma 1-14</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>H&lt;sub&gt;2&lt;/sub&gt;PtCl&lt;sub&gt;6&lt;/sub&gt; 6H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>Ar; Ar/CO gases</td><td>Air Liquid</td><td></td><td></td></tr><tr><td>Uranium and Plutonium compounds</td><td></td><td></td><td>Prepared in the laboratories of Marcoule Research Center</td></tr><tr><td>Perchloric acid</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>Phosphoric acid</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>Formic acid</td><td>Sigma-Aldrich</td><td></td><td></td></tr></tbody></table>

activating molecules, ions, and solid particles with acoustic cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Uranyl ion sonoluminescence is extremely weak in HClO4 solutions: though typical light absorption by UO22+ ions is observed below 500 nm, emission lines from excited (UO22+)* (centered at 512 nm and 537 nm) are hardly seen (Figure 1). The SL of UO22+ is quenched. This quenching can be attributed to reduction of the excited uranyl ion by a coordinated water molecule 11-13:
(...

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Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

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15.0K Views.  UMR 5257 CEA-CNRS-UM2-ENSCM. Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

Video: Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

Acoustofluidic devices use ultrasonic waves within microfluidic channels to manipulate, concentrate and isolate suspended micro and nanoscopic entities. This protocol describes the fabrication and operation of such a device supporting bulk acoustic standing waves to focus particles in a central streamline without the aid of sheath fluids.

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

Engineering

Controllable Nucleation of Cavitation from Plasmonic Gold Nanoparticles for Enhancing High Intensity Focused Ultrasound Applications

In this study, plasmonic gold nanoparticles were simultaneously exposed to pulsed near-infrared laser light and high intensity focused ultrasound (HIFU) for the controllable nucleation of cavitation in tissue-mimicking gel phantoms. This in vitro protocol was developed to demonstrate the feasibility of this approach, for both enhancement of imaging and therapeutic applications for cancer. The same apparatus can be used for both imaging and therapeutic applications by varying the exposure duration of the HIFU system. For short duration exposures (10 &#181;s), broadband acoustic emissions were generated through the controlled nucleation of inertial cavitation around the gold nanoparticles. These emissions provide direct localization of nanoparticles. For future applications, these particles may be functionalized with molecular-targeting antibodies (e.g. anti-HER2 for breast cancer) and can provide precise localization of cancerous regions, complementing routine diagnostic ultrasound imaging. For continuous wave (CW) exposures, the cavitation activity was used to increase the localized heating from the HIFU exposures resulting in larger thermal damage in the gel phantoms. The acoustic emissions generated from inertial cavitation activity during these CW exposures was monitored using a passive cavitation detection (PCD) system to provide feedback of cavitation activity. Increased localized heating was only achieved through the unique combination of nanoparticles, laser light and HIFU. Further validation of this technique in pre-clinical models of cancer is necessary.

This protocol demonstrates the controllable nucleation of cavitation in gel phantoms, through simultaneous exposure to both near-infrared pulsed laser light and high intensity focused ultrasound (HIFU). The cavitation activity can then be used for enhancing imaging and/or therapeutic uses of HIFU.

In this study, plasmonic gold nanoparticles were simultaneously exposed to pulsed near-infrared laser light and high intensity focused ultrasound (HIFU) ...

Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations

We demonstrate a method for increasing the tuning ability of a standing surface acoustic wave (SSAW) for microparticles manipulation in a lab-on-a-chip (LOC) system. The simultaneous excitation of the fundamental frequency and its third harmonic, which is termed as dual-frequency excitation, to a pair of interdigital transducers (IDTs) could generate a new type of standing acoustic waves in a microfluidic channel. Varying the power and the phase in the dual-frequency excitation signals results in a reconfigurable field of the acoustic radiation force applied to the microparticles across the microchannel (e.g., the number and location of the pressure nodes and the microparticle concentrations at the corresponding pressure nodes). This article demonstrates that the motion time of the microparticle to only one pressure node can be reduced ~2-fold at the power ratio of the fundamental frequency greater than ~90%. In contrast, there are three pressure nodes in the microchannel if less than this threshold. Furthermore, adjusting the initial phase between the fundamental frequency and the third harmonic results in different motion rates of the three SSAW pressure nodes, as well as in the percentage of microparticles at each pressure node in the microchannel. There is a good agreement between the experimental observation and the numerical predictions. This novel excitation method can easily and non-invasively integrate into the LOC system, with a wide tenability and only a few changes to the experimental set-up.

A protocol for manipulating the microparticles in a microfluidic channel with a dual-frequency excitation is presented.

We demonstrate a method for increasing the tuning ability of a standing surface acoustic wave (SSAW) for microparticles manipulation in a lab-on-a-chip ...

Induction of Microstreaming by Nonspherical Bubble Oscillations in an Acoustic Levitation System

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. Experimental observations suggest that the temporary permeabilization of these barriers may be due to shear stress that is exerted on cell tissues by cavitation microstreaming. Cavitation microstreaming is the generation of vortex flows which arise around oscillating ultrasound microbubbles. To produce such liquid flows, bubble oscillations must deviate from purely spherical oscillations and include either a translational instability or shape modes. Experimental studies of bubble-induced flows and shear stress on nearby surfaces are often restricted in their scope due to the difficulty of capturing shape deformations of microbubbles in a stable and controllable manner. We describe the design of an acoustic levitation chamber for the study of symmetry-controlled nonspherical oscillations. Such control is performed by using a coalescence technique between two approaching bubbles in a sufficiently intense ultrasound field. The control of nonspherical oscillations opens the way to a controlled cavitation microstreaming of a free surface-oscillating microbubble. High-frame rate cameras allow investigating quasi-simultaneously the nonspherical bubble dynamics at the acoustic timescale and the liquid flow at a lower timescale. It is shown that a large variety of fluid patterns may be obtained and that they are correlated to the modal content of the bubble interface. We demonstrate that even the high-order shape modes can create large-distance fluid patterns if the interface dynamics contain several modes, highlighting the potential of nonspherical oscillations for targeted and localized drug delivery.

A fast and reliable technique is proposed to control the shape oscillations of a single, trapped acoustic bubble that is based on coalescence technique between two bubbles. The steady-state, symmetry-controlled bubble shape oscillations allow analysis of the fluid flow generated in the vicinity of the bubble interface.

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. ...

A Microfluidic System with Surface Patterning for Investigating Cavitation Bubble(s)&#8211;Cell Interaction and the Resultant Bioeffects at the Single-cell Level

In this manuscript, we first describe the fabrication protocol of a microfluidic chip, with gold dots and fibronectin-coated regions on the same glass substrate, that precisely controls the generation of tandem bubbles and individual cells patterned nearby with well-defined locations and shapes. We then demonstrate the generation of tandem bubbles by using two pulsed lasers illuminating a pair of gold dots with a few-microsecond time delay. We visualize the bubble-bubble interaction and jet formation by high-speed imaging and characterize the resultant flow field using particle image velocimetry (PIV). Finally, we present some applications of this technique for single cell analysis, including cell membrane poration with macromolecule uptake, localized membrane deformation determined by the displacements of attached integrin-binding beads, and intracellular calcium response from ratiometric imaging. Our results show that a fast and directional jetting flow is produced by the tandem bubble interaction, which can impose a highly localized shear stress on the surface of a cell grown in close proximity. Furthermore, different bioeffects can be induced by altering the strength of the jetting flow by adjusting the standoff distance from the cell to the tandem bubbles.

A microfluidic chip was fabricated to produce pairs of gold dots for tandem bubble generation and fibronectin-coated islands for single-cell patterning nearby. The resultant flow field was characterized by particle image velocimetry and was employed to study various bioeffects, including cell membrane poration, membrane deformation, and intracellular calcium response.

In this manuscript, we first describe the fabrication protocol of a microfluidic chip, with gold dots and fibronectin-coated regions on the same glass ...

Bioengineering

Generation and Quantitative Analysis of Pulsed Low Frequency Ultrasound to Determine the Sonic Sensitivity of Untreated and Treated Neoplastic Cells

Low frequency ultrasound in the 20 to 60 kHz range is a novel physical modality by which to induce selective cell lysis and death in neoplastic cells. In addition, this method can be used in combination with specialized agents known as sonosensitizers to increase the extent of preferential damage exerted by ultrasound against neoplastic cells, an approach referred to as sonodynamic therapy (SDT). The methodology for generating and applying low frequency ultrasound in a preclinical in vitro setting is presented to demonstrate that reproducible cell destruction can be attained in order to examine and compare the effects of sonication on neoplastic and normal cells. This offers a means by which to reliably sonicate neoplastic cells at a level of consistency required for preclinical therapeutic assessment. In addition, the effects of cholesterol-depleting and cytoskeletal-directed agents on potentiating ultrasonic sensitivity in neoplastic cells are discussed in order to elaborate on mechanisms of action conducive to sonochemotherapeutic approaches.

Selective damage of human leukemia cells can be achieved through a novel approach of applying low frequency ultrasound both with and without chemotherapeutic pretreatment of leukemic and normal hematopoietic cells.

Low frequency ultrasound in the 20 to 60 kHz range is a novel physical modality by which to induce selective cell lysis and death in neoplastic cells. In ...

Medicine

Imaging and Quantification of the Area of Fast-Moving Microbubbles Using a High-Speed Camera and Image Analysis

An experimental and image analysis technique is presented for imaging cavitation bubbles and calculating their area. The high-speed imaging experimental technique and image analysis protocol presented here can also be applied for imaging microscopic bubbles in other fields of research; therefore, it has a wide range of applications. We apply this to image cavitation around dental ultrasonic scalers. It is important to image cavitation to characterize it and to understand how it can be exploited for various applications. Cavitation occurring around dental ultrasonic scalers can be used as a novel method of dental plaque removal, which would be more effective and cause less damage than current periodontal therapy techniques. We present a method for imaging the cavitation bubble clouds occurring around dental ultrasonic scaler tips using a high-speed camera and a zoom lens. We also calculate the area of cavitation using machine learning image analysis. Open source software is used for image analysis. The image analysis presented is easy to replicate, does not require programming experience, and can be modified easily to suit the application of the user.

Cavitation microbubbles are imaged using a high-speed camera attached to a zoom lens. The experimental setup is explained, and image analysis is used to calculate the area of the cavitation. Image analysis is done using ImageJ.

An experimental and image analysis technique is presented for imaging cavitation bubbles and calculating their area. The high-speed imaging experimental ...

Studying Cavitation Enhanced Therapy

Interest in the therapeutic applications of ultrasound is significant and growing, with potential clinical targets ranging from cancer to Alzheimer&#8217;s disease. Cavitation - the formation and subsequent motion of bubbles within an ultrasound field - represents a key phenomenon underpinning many of these treatments. There remains, however, considerable uncertainty regarding the detailed mechanisms of action by which cavitation promotes therapeutic effects and there is a need to develop reliable monitoring techniques that can be implemented clinically. In particular, there is significant variation between studies in the exposure parameters reported as successfully delivering therapeutic effects and the corresponding acoustic emissions. The aim of this paper is to provide design guidelines and an experimental protocol using widely available components for performing studies of cavitation-mediated bioeffects, and&#160;include real-time acoustic monitoring. It is hoped that the protocol will enable more widespread incorporation of acoustic monitoring into therapeutic ultrasound experiments and facilitate easier comparison across studies of exposure conditions and their correlation to relevant bio-effects.

The presented experimental protocol can be used to perform real time measurements of cavitation activity in a cell culture device with the aim of enabling investigation of the conditions required for successful drug delivery and/or other bioeffects.

Interest in the therapeutic applications of ultrasound is significant and growing, with potential clinical targets ranging from cancer to ...

Assembly and Operation of an Acoustofluidic Device for Enhanced Delivery of Molecular Compounds to Cells

Efficient intracellular delivery of biomolecules is required for a broad range of biomedical research and cell-based therapeutic applications. Ultrasound-mediated sonoporation is an emerging technique for rapid intracellular delivery of biomolecules. Sonoporation occurs when cavitation of gas-filled microbubbles forms transient pores in nearby cell membranes, which enables rapid uptake of biomolecules from the surrounding fluid. Current techniques for in vitro sonoporation of cells in suspension are limited by slow throughput, variability in the ultrasound exposure conditions for each cell, and high cost. To address these limitations, a low-cost acoustofluidic device has been developed which integrates an ultrasound transducer in a PDMS-based fluidic device to induce consistent sonoporation of cells as they flow through the channels in combination with ultrasound contrast agents. The device is fabricated using standard photolithography techniques to produce the PDMS-based fluidic chip. An ultrasound piezo disk transducer is attached to the device and driven by a microcontroller. The assembly can be integrated inside a 3D-printed case for added protection. Cells and microbubbles are pushed through the device using a syringe pump or a peristaltic pump connected to PVC tubing. Enhanced delivery of biomolecules to human T cells and lung cancer cells is demonstrated with this acoustofluidic system. Compared to bulk treatment approaches, this acoustofluidic system increases throughput and reduces variability, which can improve cell processing methods for biomedical research applications and manufacturing of cell-based therapeutics.

This protocol describes the assembly and operation of a low-cost acoustofluidic device for rapid molecular delivery to cells via sonoporation induced by ultrasound contrast agents.