Transition from liquid droplet to solid particle investigated by ultrasonic spectroscopy.

The size distribution and elastic modulus of micron-sized particles dispersed in liquid can be quantitatively evaluated by ultrasonic spectroscopy at a megahertz frequency range combined with a scattering theory. Conventional theories dealing with the wavelength comparable with the micron-sized particles consider viscosity for liquid droplets in emulsions and elasticity for solid particles in suspension, but very few studies have simultaneously considered viscosity and elasticity for the dispersed phase. In this study, a toluene (Tol) solution of polystyrene (PS) was dispersed in a continuous phase (water), and the ultrasonic properties of the PS-Tol/water emulsion were investigated.

Interfacial structures of particle-stabilized emulsions examined by ultrasonic scattering analysis with a core-shell model.

Pickering emulsions comprising liquid droplets stabilized by solid microparticles have gained much attention in the field of cosmetics, inks, and drug delivery systems. To ensure that microparticles in Pickering emulsions are localized at the surface of liquid droplets, ultrasonic spectroscopy analysis combined with scattering function theory was conducted in this study. Two specific cases were investigated: (1) silica particles and liquid droplets independently dispersed in liquid and (2) silica particles effectively localized at the surface of the droplets.

Viscoelastic ECAH: Scattering analysis of spherical particles in suspension with viscoelasticity.

Ultrasonic scattering method is a promising technique to evaluate the particle size distribution and/or the elastic properties of particle suspended in liquid. Among the wide variety of scattering theories, the ECAH theory proposed by Epstein-Carhart-Allegra-Hawley is one of the most relevant acoustic scattering theories to reproduce the ultrasonic spectroscopy data for the particle suspensions. However, the original theory assumes that the shear contribution is provided for either elastic solid or viscous liquid.

Simultaneous measurements of ultrasound attenuation, phase velocity, thickness, and density spectra of polymeric sheets.

The size distribution and mechanical properties of microparticle dispersed in liquid can be characterized by ultrasonic spectroscopy with the aid of acoustic scattering theories. In order to carry out the accurate analysis of the particles, the basic properties, such as the density, viscosity, longitudinal and shear velocities and intrinsic attenuation coefficient of the particle must be known prior to the analysis. Particularly, for soft elastomers or rubbers which exhibit complex mechanical properties with comparable real and imaginary parts, such fundamental information should be provided prior to the particle analysis to minimize the uncertainty of estimation associated with the number of adjustable parameters.