Under the action of ultrasonic energy, two or more immiscible liquids are mixed together, and one of the liquids is relatively uniformly dispersed in the other liquid to form an emulsion liquid, and this 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, the liquid ruptures at the point where the cohesion is weaker. After this rupture, overpressure appeared at the point where the rupture occurred, and some cavities were found. In these cavities, the liquid dissolved gas explodes in the form of bubbles after a short time.
In order to stabilize the newly formed dispersed phase droplets to prevent coalescence, emulsifiers (surface active substances, surfactants) and stabilizers are added to the emulsion. The final droplet size distribution is maintained at the same level as when the droplets are ruptured in the ultrasonic dispersion zone.
The cavitation process is affected by the frequency and intensity of ultrasonic waves. The appearance of cavitation in the body depends to a large extent on the existence of undissolved gas in the liquid suspension. The existence of the gas seems to act as a catalyst. Under a certain pressure, the formation of the cavity depends to a certain extent on the development time and the ultrasonic frequency. The phacoemulsification process represents a competition between opposing processes. Therefore, it is necessary to select suitable working conditions and frequencies so that the destructive effects dominate.
Ultrasonic cavitation effect
To prepare an oil-in-water emulsion, its 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 applying some stationary waves, the process efficiency is improved. This can be explained by the fact that in a static wave field, the opposite process of dispersion, namely condensation, is dominant.
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