Change of evaporation rate of single monocomponent droplet with temperature using time-resolved phase rainbow refractometry

International audienc

Nanoshells for photothermal therapy: a Monte-Carlo based numerical study of their design tolerance

The optimization of the coated metallic nanoparticles and nanoshells is a current challenge for biological applications, especially for cancer photothermal therapy, considering both the continuous improvement of their fabrication and the increasing requirement of efficiency. The efficiency of the coupling between illumination with such nanostructures for burning purposes depends unevenly on their geometrical parameters (radius, thickness of the shell) and material parameters (permittivities which depend on the illumination wavelength). Through a Monte-Carlo method, we propose a numerical study of such nanodevice, to evaluate tolerances (or uncertainty) on these parameters, given a threshold of efficiency, to facilitate the design of nanoparticles. The results could help to focus on the relevant parameters of the engineering process for which the absorbed energy is the most dependant. The Monte-Carlo method confirms that the best burning efficiency are obtained for hollow nanospheres and exhibit the sensitivity of the absorbed electromagnetic energy as a function of each parameter. The proposed method is general and could be applied in design and development of new embedded coated nanomaterials used in biomedicine applications

Caractérisation du givrage par réfractométrie d'arc-en-ciel

International audienceLa caractérisation des propriétés thermo-chimiques (température et composition) de particules en écoulement est un défi, riche d’applications académiques et industrielles dans de nombreux domaines comme la combustion [1], les moteurs d’avions, le givrage, les sécheurs de sprays, la chimie hétérogène [2, 3]... Pour relever ce défi, l’une des solutions est de mesurer l’indice de réfraction des gouttes, puis de relier cet indice de réfraction à la température ou à la composition de celles-ci. La société RainbowVision a développé un tel appareil, basé sur l’analyse de la lumière diffusée aux alentours de l’angle d’arc-en-ciel. Cet appareil permet la mesure précise de l’indice de réfraction moyen, donc de la température et/ou de la composition, et de la distribution de taille de gouttes en écoulement. Un domaine où la connaissance de la température des gouttes est particulièrement important est celui du givrage. En effet recréer les condition naturelles du givrage dans une soufflerie est un défi, riche d’applications industrielles (sécurité des avion, réallumage en vol, ..). Une difficulté importante est la détermination de la température des gouttes d’eau. Dans la nature, le temps de séjours des gouttes est long, donc la température des gouttes peut être supposée égale à celle de l’air. Dans une soufflerie froide, les gouttes doivent être injectées à une température positive, puis voyagent sur quelques mètres, ce qui correspond à un temps de séjours cours, limitant les échanges de température entre les gouttes et l’air. La mesure de la température et de la distribution de taille des gouttes avant l’impact sur un obstacle est donc cruciale pour la caractérisation du givrage. Le but de cet article est de présenter et de valider une technique permettant de mesurer la température et la distribution de taille de gouttes d’eau dans une soufflerie froide

Interferometric out-of-focus imaging simulator for irregular rough particles

We present the development of an original simulator to predict interferometric out-of-focus patterns created by irregular rough particles. Despite important simplifications of the scattering properties, this simulator allows to predict quantitative properties of the speckle-like patterns: i.e. the dimension of the central peak of the 2D-autocorrelation of the pattern. This parameter can then be linked to the size and the shape of the particle projected on the CCD sensor, in cases where there is no exact theoretical formulation to calculate the scattered intensity. An experimental demonstration is performed with irregular NaCl salt crystals

Determination of the Size of Irregular Particles Using Interferometric Out-of-Focus Imaging

We present a mathematical formalism to predict speckle-like interferometric out-of-focus patterns created by irregular scattering objects. We describe the objects by an ensemble of Dirac emitters. We show that it is not necessary to describe rigorously the scattering properties of an elliptical irregular object to predict some physical properties of the interferometric out-of-focus pattern. The fit of the central peak of the 2D autocorrelation of the pattern allows the prediction of the size of the scattering element. The method can be applied to particles in a size range from a tenth of micrometers to the millimeter

Mesures d'évaporation par suivi de taille de gouttes à l'échelle nanométrique en imagerie interférométrique

International audienc

Simultaneous measurement of monocomponent droplet temperature/refractive index, size and evaporation rate with phase rainbow refractometry

International audienc

Primary rainbow of high refractive index particle (1.547 < n < 2) has refraction ripples

International audienc

Digital in-line holography assessment for general phase and opaque particle

We propose using the circle polynomials to describe a particle’s transmission function in a digital holography setup. This allows both opaque and phase particles to be determined. By means of this description, we demonstrate that it is possible to estimate the digital in-line hologram produced by a spherical particle. The experimental intensity distribution due to an opaque micro-inclusion is compared to the theoretical one obtained by our new model. Moreover, the simulated hologram and reconstructed image of the particle by an optimal fractional Fourier transformation under the opaque disk, quadratic phase, and quasi-spherical phase approximation are compared with the results obtained by simulating holograms by the Lorenz–Mie Theory (LMT). The Zernike coefficients corresponding to the considered particles are evaluated using the double exponential (DE) method which is optimal in various respects