Principle of Ultrasonic Emulsification
Under the action of ultrasonic energy, two or more immiscible liquids are mixed together. One of the liquids is also relatively uniformly dispersed in the other liquid, forming an emulsion-like liquid. This process is called ultrasonic emulsification.
Phacoemulsification is caused by cavitation. Ultrasound passing through the liquid causes it to continuously compress and expand. High intensity ultrasound provides the energy needed to disperse the liquid phase. When the maximum pressure is reached, liquid rupture occurs at the point where the cohesion is weak. After this rupture, overpressure occurred at the point where the rupture occurred, and some cavities were found. In these voids, the liquid-dissolved gas explodes in the form of bubbles shortly after.
To stabilize the newly formed dispersed phase droplets to prevent coalescence, emulsifiers (surfactants, surfactants) and stabilizers are added to the emulsion. The final droplet size distribution was maintained at the same level as when the droplets were distributed in the ultrasonic dispersion zone.
The cavitation process is affected by the frequency and intensity of ultrasonic waves. The occurrence of cavitation in the body depends to a large extent on the presence of undissolved gas in the liquid suspension. The presence of the gas seems to play a catalyst role. Under certain pressure, the formation of the cavity depends to some extent on the development time and the frequency of the ultrasound. The phacoemulsification process represents competition between opposing processes. Therefore, it is necessary to choose the appropriate working conditions and frequency so that the destruction effects dominate.
Ultrasonic cavitation effect
To prepare an oil-in-water emulsion, the ultimate sound intensity is much lower than that of a water-in-oil emulsion. The type of sound field affects the emulsification process, that is, a certain traveling wave is applied. Compared with the application of some stationary waves, the process efficiency is improved. This can be explained by the fact that in a stationary wave field, the process opposite to dispersion, that is, condensation is dominant.