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We present two routes of millifluidic-based synthesis of solid core-solid shell particles with submillimeter size. These particles, which behave as mechanical resonators, are key components of targeted three-dimensional locally resonant acoustic metamaterials working in the ultrasonic frequency range. The first route involves the encapsulation of a solid core into a liquid shell, which is then in-line solidified through gelation. The second route involves two successive coflows followed by two solidifications triggered by UV irradiation and complexation, respectively. Original solutions to several practical issues are presented. The advantages and drawbacks of both routes are analyzed in the light of the targeted specifications of the resonators. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

We study flows and interface deformations produced by the scattering of a laser beam propagating through non-absorbing turbid fluids. Light scattering produces a force density resulting from the transfer of linear momentum from the laser to the scatterers. The flow induced in the direction of the beam propagation, called ‘optical streaming’, is also able to deform the interface separating the two liquid phases and to produce wide humps. The viscous flow taking place in these two liquid layers is solved analytically, in one of the two liquid layers with a stream function formulation, as well as numerically in both fluids using a boundary integral element method. Quantitative comparisons are shown between the numerical and analytical flow patterns. Moreover, we present predictive simulations regarding the effects of the geometry, of the scattering strength and of the viscosities, on both the flow pattern and the deformation of the interface. Finally, theoretical arguments are put forth to explain the robustness of the emergence of secondary flows in a two-layer fluid system. [ABSTRACT FROM AUTHOR]

We present an analytical model of the time-dependent, small-amplitude deformation of a free liquid surface caused by a spatially localized, axisymmetric, pulsed or continuous, acoustic or electromagnetic radiation pressure exerted on the surface. By exactly solving the unsteady Stokes equation, we predict the surface dynamics in all dynamic regimes, namely inertial, intermediate and strongly damped regimes. We demonstrate the validity of this model in all dynamic regimes by comparing its prediction to experiments consisting of optically measuring the time-dependent curvature of the tip of a hump created at a liquid surface by the radiation pressure of an acoustic pulse. Finally, we present a numerical scheme simulating the behaviour of a fluid–fluid interface subjected to a time-dependent radiation pressure and show its accuracy by comparing the numerical predictions with the analytical model in the intermediate and strongly damped regimes. [ABSTRACT FROM PUBLISHER]

We report on the direct experimental observation of laser-induced flows in isotropic liquids that scatter light. We use a droplet microemulsion in the two-phase regime, which behaves like a binary mixture. Close to its critical consolute line, the microemulsion undergoes large refractive index fluctuations that scatter light. The radiation pressure of a laser beam is focused onto the soft interface between the two phases of the microemulsion and induces a cylindrical liquid jet that continuously emits droplets. We demonstrate that this dripping phenomenon takes place as a consequence of a steady flow induced by the transfer of linear momentum from the optical field to the liquid due to light scattering. We first show that the cylindrical jet guides light as a step-index liquid optical fiber whose core diameter is self-adapted to the light itself. Then, by modelling the light-induced flow as a low-Reynolds-number, parallel flow, we predict the dependence of the dripping flow rate on the thermophysical properties of the microemulsion and the laser beam power. Satisfying agreement is found between the model and experiments. [ABSTRACT FROM AUTHOR]

We report on the observation of the periodic pattern occuring in a two-dimensional (2D) assembly of heavy beads (of diameter D = 280-630/µm) immersed in water when the vessel containing the fluid and the beads is submitted to horizontal vibrations (of frequency f and oscillation amplitude A). Under vibrations, regularly spaced, one bead thick lines perpendicular to the direction of vibrations are formed at small surface fraction. In the ranges f = 10-20 Hz and A = 0.7-3.5 mm, the amplitude of the oscillatory motion of the beads relative to the fluid B is found to vary linearly with A. A simple phenomenological model based on dynamic solid friction and viscous drag gives qualitatively account for this linear dependence. The period of the pattern X is found to vary with viscosity υ, ω=2πf, D, and B according to the law λ/D∼(B/D)[sup 0.5](BωD/υ)[sup -0.21]. The dynamics of pattern formation exhibits several scenarii, depending on the initial bead distribution, as well as several characteristic time scales. We review and discuss possible mechanisms of pattern formation reported in literature and proposed for similar phenomena observed in the frame of rheology of suspensions and acoustic streaming flows. [ABSTRACT FROM AUTHOR]

The optical index constants of CO[sub 2] at critical density are measured by terahertz (THz) time-domain spectroscopy (TDS–THz) in the frequency range 0.1–1.5 THz. Since supercritical CO[sub 2] is usually presented as a “universal” solvent, we systematically study the refractive index variations in the vicinity of its critical point along the critical isochore by scanning temperature from 295 to 308 K to explore the liquid, the gas, and the supercritical states. Density changes with temperature result in refractive index variations that are found to fit the Lorenz–Lorentz relationship in the THz frequency range. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on two instabilities, called viscous fountain and viscous entrainment, triggered at the interface between two liquids by the action of bulk flows driven by a laser beam. These streaming flows are due to light scattering losses in turbid liquids, and can be directed either toward or forward the interface. We experimentally and numerically investigate these interface instabilities and show that the height and curvature of the interface deformation at the threshold and the jet radius after interface destabilization mainly depend on the waist of the laser beam. Analogies and differences between these two instabilities are characterized. [ABSTRACT FROM AUTHOR]

We unveil the generation of universal morphologies of fluid interfaces by radiation pressure regardless of the nature of the wave, whether acoustic or optical. Experimental observations reveal interface deformations endowed with steplike features that are shown to result from the interplay between the wave propagation and the shape of the interface. The results are supported by numerical simulations and a quantitative interpretation based on the waveguiding properties of the field is provided. [ABSTRACT FROM AUTHOR]

A study is presented concerning an experiment under weightlessness. A pure fluid (SF6) is heated near and below its critical point, where liquid coexists with vapor. After the temperature rise, the vapor phase passes well beyond the temperature of the heating walls. This surprising finding is discussed in the light of an adiabatic heat transfer or “Piston effect” and the special geometry of the liquid and vapor. In addition, the shape of the gas–liquid interface is distorted near the solid wall by the thrust of vapor production (“recoil” force), a precursor to the well-known boiling crisis in heat exchanger. [Copyright &y& Elsevier]

We quantitatively report on the rotational mechanical effect of wave orbital angular momentum on matter by nondissipative vortex mode conversion. Our experiments consist of ultrasonic waves reflected off freely spinning helical acoustic mirrors that are capillary trapped at a curved air-water interface. Considering helical mirrors with integer topological charges these results represent the demonstration of the experiment proposed by Allen et al. originally introduced in the optical domain [Phys. Rev. A 45, 8185 (1992)], whose quantitative implementation remains elusive to date whatever the nature of the wave. The study is further generalized to helical mirrors with fractional charges. [ABSTRACT FROM AUTHOR]

We have reproduced the experiment of acoustic monitoring of spontaneous popping of single soap bubbles standing in air reported by Ding et al. [Phys. Rev. E 75, 041601 (2007)]. By using a single microphone and two different signal acquisition systems recording in parallel the signal at the microphone output, among them the system used by Ding et al., we have experimentally evidenced that the acoustic precursors of bubble popping events detected by Ding et al. actually result from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. No acoustic precursor of popping couid be evidenced with the microphone used in these experiments, whose sensitivity is 1 VPa-1 and frequency range is 500 Hz-100 kHz. [ABSTRACT FROM AUTHOR]