Localized high pressure near an aspheric encapsulated microbubble

Abstract

Based on hydrodynamics, the pressure of the liquid outside an aspheric encapsulated bubble driven by ultrasound is studied, and its analytical expression is derived. Numerical simulation shows that 1) the aspheric shape of an encapsulated bubble makes little influence on the pressure of the liquid far away from the bubble; 2) the pressure is extremely high at some local places of the liquid near an aspheric encapsulated bubble, and the pressure values at these places are apparently larger than those for a spherical encapsulated bubble at the same conditions. This phenomenon is of significance in the applications such as high intensity ultrasound therapy, drug delivery, cell membrane perforation, etc. As the ultrasound frequency shifts to the resonance frequency of an encapsulated bubble, or bubble shape deviates from sphericity, the localized high pressure becomes even greater.