Nanodroplets have great, promising medical applications such as contrast imaging, embolotherapy, or targeted drug delivery. Their functions can be mechanically activated by means of focused ultrasound inducing a phase change the inner liquid known acoustic droplet vaporization (ADV) process. In this context, four-phases (vapor + shell surrounding environment) model ADV is proposed. Attention especially devoted to mechanical properties encapsulating shell, incorporating well-known...

While numerous theoretical studies exist on microstreaming around acoustically excited, trapped gas bubbles, experimental approaches have mainly been conducted for bubbles attached to a solid boundary. One of the main difficulties lies in positional stability microbubble. In present work we trigger surface modes by bubble coalescence, with advantage limiting translational instabilities and controlling orientation axisymmetric deformation. Furthermore, streaming is visualised fluorescent...

We report observations of strong nonlinear interactions between the spherical, translational, and shape oscillations micrometer-size bubbles. This is achieved through high-speed recordings single bubble dynamics driven by amplitude-modulated ultrasound. The features mode coupling are highlighted (i) exponential growth parametrically excited ($n=3$) triggered spherical followed a saturation due to energy transfer towards translation even modes, (ii) excitation modes well below their...

Time-resolved dynamics of nonspherical oscillations micrometer-sized bubbles are captured and analyzed using high-speed imaging. The axisymmetry the bubble shape is ensured with certainty for first time from recordings two synchronous cameras located at ${90}^{\ensuremath{\circ}}$. temporal finite-amplitude then various acoustic pressures above instability threshold. experimental results compared recent theories accounting nonlinearities mode coupling, highlighting particular effects...

The aim of this paper is to propose a method predict the onset conditions thermoacoustic instability for various engines. As an accurate modeling heat exchangers and stack submitted temperature gradient difficult task, experimental approach characterization amplifying properties core proposed. An apparatus presented which allows measure transfer matrix under heating by means four-microphone method. analytical model prediction from measured developed. data are introduced in theoretical...

The use of encapsulated liquid nanoparticles is currently largely investigated for medical applications, mainly because their reduced size allows them to enter targeted areas which cannot be reached by large microbubbles (contrast agents). Low-boiling point perfluorocarbon droplets can vaporized on-site under the action ultrasonic field, in order turn into echogeneous—eventually cavitating—microbubbles. This paper presents a theoretical model describing this phenomenon, paying particular...

A model for the description of transient regime leading to steady-state sound in a quarter-wavelength thermoacoustic prime mover is proposed, which based on unsteady heat transfer system, coupled with an ordinary differential equation describing wave amplitude growth/attenuation. The equations are derived by considering cross-sectional averaged temperature distribution along resonator, and assuming that both characteristic time associated diffusion through stack amplification much larger...

Shape oscillations arising from the spherical instability of an oscillating bubble can be sustained in a stationary acoustic field. Describing such steady state requires that nonlinear saturation effects are accounted for to counteract natural exponential growth instability. In this paper, we analyse establishment finite-amplitude shape as consequence interactions between and non-spherical modes. The set coupled dynamical equations describing volume pulsation is solved using perturbation...

When two bubbles encounter each other in a moderate ultrasound field they coalesce into single bubble that shows purely spherical oscillations. For sufficiently large acoustic field, this coalescence can lead to sustained nonspherical oscillations of the resulting bubble. We experimentally capture time-resolved dynamics coalesced bubble, starting with moment film rupture. This allows transient and steady-state regimes oscillating be studied. The amplitude for both these are successfully...

Liquid droplets of nanometric size encapsulated by a polymer shell are envisioned for targeted drug delivery in therapeutic applications. Unlike standard micrometric gas-filled contrast agents used medical imaging, these particles present thick and weakly compressible core. Hence, their dynamical behavior may be out the range validity models available description bubbles. In paper, model ultrasound dispersion absorption suspension nanodroplets is proposed, accounting both dilatational...

Abstract Transparent thin‐film piezoelectric transducers are attractive for haptic displays. However, their widespread use in consumer electronics, innovative and cost‐effective processing methods need to be developed. In this contribution the effectiveness of deposition lead zirconate titanate thin films by inkjet printing fabrication devices is demonstrated. The 1,3‐propanediol solvent used prepare effective inkjet‐printing inks from chemical solution solutions. printed structures on fused...

The oscillations of a single bubble excited with dual frequency acoustic field are numerically investigated. Computations made for an air in water exposed to linearly varying amplitude. response excitation containing two frequencies f1 = 500kHz and f2 400kHz at the same amplitude is compared monofrequency case where only present. Time-frequency representations show sharp transition bifrequency case, which low component becomes resonant while high strongly attenuated. temporal evolution power...

We use ultrasound spectroscopy to determine viscosity, radii and shell thickness distribution of nanoparticles in suspension.

A potential source of subharmonic bubble emissions is revealed experimentally by high-speed imaging. When an acoustic driven at sufficiently large pressure amplitudes, energy transfer from surface to volume oscillations can lead the triggering spherical oscillations. This experimental evidence in agreement with recent theoretical modeling nonspherical dynamics accounting for nonlinear mode coupling. Implications monitoring stable cavitation activity are discussed.

Bubbles insonified by ultrasound can exhibit shape deformations and no more oscillate upon a purely spherical mode. Understanding predicting the appearance of surface oscillations is essential for typical applications based on acoustic response bubbles (e.g. use contrast agents in echographic imaging), partly because modes contribute to monopole emission sound bubble. In this work, we present set controlled experiments aiming at recording high-resolved temporal dynamics micrometer-sized...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Matthieu Guédra, Cyril Desjouy, Claude Inserra, Jean-Christophe Béra, Bruno Gilles; Theoretical investigation of the mechanisms involved in modification cavitation threshold by multifrequency excitations. AIP Conference Proceedings 28 October 2015; 1685 (1): 050003. https://doi.org/10.1063/1.4934419 Download...

Microbubbles exposed to a sufficiently strong ultrasound field can show nonspherical oscillations called surface modes. In the vicinity of bubble surface, these induce slow mean flow named microstreaming. Microstreaming plays an important role in medical applications such as sonoporation well engineering micromixing. A better understanding induced flows will hence be beneficial large number applications. Recent studies mainly report on microstreaming by bubbles resting solid boundary. The...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Guillaume Penelet, Matthieu Guedra, Vitalyi Gusev; Account of heat convection by Rayleigh streaming in the description wave amplitude growth stabilization a standing thermoacoustic prime-mover.. AIP Conference Proceedings 4 September 2012; 1474 (1): 291–294. https://doi.org/10.1063/1.4749353 Download citation...

Several analytical or numerical models available in the litterature allow to predict onset of thermoacoustic engines [5, 6, 11]. However, most these rely on strong assumptions concerning for instance stack geometry shape temperature field core. The purpose work presented here is put forward a new method allowing prediction instability while being exempted from certain number assumptions. This consists measuring transfer matrix core by means an appropriate experimental setup developed our...