Non-Contact Micro-Liquid Mixing Method Using Ultrasound(<Special Issue>Advanced Fluid Information)

A new mixing method for micro-liquid has been developed. In the new method, a radiation pressure of ultrasound is used to stir liquid in a vessel without any physical contact. The developed mixing device based on the method consists of a vessel containing the liquid to be mixed and two ultrasound sources (frequency: 1.6MHz) arranged outside the vessel. One of them radiates through the bottom, the other through the side wall of the vessel. The latter sound source is divided into several segments. And the fine position of the sound source corresponding to the level of liquid is adjusted by selecting the appropriate segments. The mixing performance is evaluated according to the difference between the two local transmissibilities of laser beam in the liquid. As a result, we confirmed that by using the mixing device, the liquid (80-160μL of water and dye) become homogeneous within 1.0 sec.