An emulsification system using a microchannel and a piezoelectric transducer

Ultrasonic emulsification devices have been used in many industrial and scientific fields. Recently, a nanoemulsion which contains small droplets having a diameter of sub-micron scale have attracted attentions. In usual, those emulsions are produced by using ultrasonic transducers oscillated to generate a cavitation field. However, such process has a difficulty to avoid contaminations. For a continuous process, we have generated the nanoemulsion by using microchannel devices and a piezoelectric transducer. The devices are made of stainless steel mainly. The micron-size droplets generated by a Y-type or T-type microchannel device, and are oscillated by a piezoelectric transducer in another microchannel device. The driving frequency of the transducer is over 2.2 MHz. We have succeeded in generating sub-micron size droplets which contain anti-cancer drug using this emulsification system. Additionally, we have evaluated the acoustic field in the microchannel by using a micro cavitation sensor. The micro sensor made of a piezoelectric polymer has been installed in the device. The sensor consists of some films deposited and patterned with a photolithography process. Using this sensor, the acoustic state in the microchannel has been evaluated from the acoustic power spectrum. From the results, we can conclude that the cavitation effect is not dominant in the emulsification process by this system.