(382b) Rheology of Fluids with Monodisperse Microbubble Suspension

Microbubbles are micron-scale hollow spheres (normally 10?200 um) with a gaseous core coated with a thin shell. Potentially, a monodisperse population of such bubbles could be introduced as part of the processing of a food. Monodisperse microbubble suspension was generated using flow focusing technique. Using this technique, we are able to control microbubble size with different flow rate ratio of air and emulsifier solution, and it lead to the ability to control the air fraction of fluids. The air entrainment and stability of this multiphase and multicomponent system are studied. Based on the fact that the microbubbles are very stable for a short time period, a rotational rheometer is used to measure the relationship of ?real time? bubble suspension rheological properties. A semi-empirical approach is used analyze the rheological behavior of this monodisperse microbubble suspension. It was revealed in the paper that the microbubble suspension shows power law rheology at low shear rate (up to 20 1/s). The viscosity of the fluids is related directly with the air fraction. Oscillation reological results also disclose the viscoelasticity of the fluids. A food grade emulsifier (mixture of monoglyceride, diglycerdie and sodium stearoyl lactylate) as well as PEG -40 was used as an alternative of pure staturated phospholipids to form the thin shell. A fluorescence microscopy technique is used to study the microstructure and dissolution behavior of these microbubbles in degassed media. Furthermore, we studied concurrently the domain features and the surface pressure-area isotherm of this emulsifier in a Langumir monolayer.