Abstract

Surfactant-stabilized microbubbles can be rapidly and easily produced in high concentrations within the narrow size range of 1-5 um. Such synthetic microbubbles, which find use in medical and other applications, persist in various aqueous media for periods up to one year. Microbubble size distribution analyses at different salt concentrations and after the addition of thiourea clearly indicate that electrostatic interactions are much less important than hydrogen bonding in stabilizing the lipid monolayer surrounding each microbubble. Direct optical confirmation of the typical (1-3 um) microbubble size and lack of bubble agglomeration was provided by phase-measurement interferometric microscopy data. In addition, freeze-fracture electron microscopy data further indicated a high degree of size uniformity for the lipid-coated microbubbles.