title: Influence of shell compressibility on the ultrasonic properties of polydispersed suspensions of nanometric encapsulated droplets.
abstract: 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 for medical imaging, these particles present a thick shell and a weakly compressible core. Hence, their dynamical behavior may be out of the range of validity of the models available for the description of encapsulated bubbles. In the present paper, a model for the ultrasound dispersion and absorption in a suspension of nanodroplets is proposed, accounting for both dilatational and translational motions of the particle. The radial motion is modeled by a generalized Rayleigh-Plesset-like equation which takes into account the compressibility of the viscoelastic shell, as well as the one of the core. The effect of the polydispersity of particles in size and shell thickness is introduced in the coupled balance equations which govern the motion of the particles in the surrounding fluid. Both effects of shell compressibility and polydispersity are quantified through the dispersion and absorption curves obtained on a wide ultrasonic frequency range. Finally, some results for larger gas-filled particles are also provided, revealing the limit of the role of the shell compressibility.
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Guédra
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors.forename: Tony
authors.initials: T
authors.lastname: Valier-Brasier
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Conoir
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS UMR 7190, Institut Jean Le Rond d'Alembert, F-75005 Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Coulouvrat
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06,CNRS UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France.
authors.forename: Ksenia
authors.initials: K
authors.lastname: Astafyeva
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06,CNRS UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Thomas
mesh_terms: D003287:Contrast Media / Q000737:chemistry; D004337:Drug Carriers; D004548:Elasticity; D005740:Gases; D016014:Linear Models; D008956:Models, Chemical; D009038:Motion; D053758:Nanoparticles; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D011312:Pressure; D013016:Sound; D014465:Ultrasonics / Q000379:methods*; D014783:Viscosity
chemical_list: D003287:Contrast Media; D004337:Drug Carriers; D005740:Gases; D011108:Polymers