Mixer cavitation

Air bubbles can be introduced in a microfluidic mixer in order to enhance the mixing process. The surface of an air bubble in a liquid medium exposed to a sound field can act as a vibrating membrane. The membrane vibration causes a bulk fluid movement at the air-hquid interface. This effect, known as cavitation microstreaming, has been applied in microfluidic micromixers using a single bubble [181] (Fig. 19) or an array of bubbles [178, 179]. 

The RUM (Reverberating Ultrasonic Mixer), with its two frequencies of 16 and 20 kHz produces a "beat" frequency of 4 kHzThe two different waves create a larger number of different cavitating bubbles than a single one. 

There are many vendors of rotor-stator mixers. The reader may refer to current editions of Thomas s Register, Chemical Engineering Buyers Guide, and so on, for an up-to-date list of major suppliers. There are a number of other suppliers whose equipment is used to produce dispersions or emulsions but which does not fit the definition of having a rotor and stator. These include high-pressure devices such as valve homogenizers, whistles, and cavitation-based devices. 

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