Tailoring the properties of ultrasonically synthesised microbubbles

Air-filled lysozyme microbubbles can be synthesized in an aqueous medium by emulsification followed by the cross-linking of protein molecules under high-intensity ultrasound. Here, we report on the tailoring of the properties of the ultrasonically synthesised microbubbles using new procedures. The efficiency of formation, size, size distribution and morphology of the microbubbles were controlled by manipulating the experimental conditions, namely, the sonication power and the length of sonication. An increase in the sonication time and power led to the formation of larger microbubbles with a broader size distribution. The microbubble shell thickness was found to decrease with an increase in the sonication power and time. Furthermore, a pulsed sonoluminescence technique was used to study the strength and stability of the microbubbles. The experimental results have shown that the effects of sonication time and power on the properties of the microbubbles are quite complex. A simple graphical matrix has been derived to obtain stable microbubbles with a narrow size distribution.