This paper reports a method to control the bubble size generated in a microfluidic flow-focusing configuration. With an ultrasonic transducer, we induce acoustic streaming using a forward moving, oscillating gas-liquid interface. The induced streaming substantially affect the formation process of gas bubbles. The oscillating interface acts as a pump that increases the gas flow rate significantly and forms a larger bubble. This method is applicable to wide range of gas pressure from 30 to 90 kPa and flow rate from 380 to 2700 mL/h. The bubble size can be tuned repeatably with a response time in the order of seconds. We believe that this method will enhance the capability of a microfluidic bubble generator to produce tunable bubble size.

Source From: Lab Chip, 2014,  DOI: 10.1039/C4LC01038H