On-Chip Virtual Vortex Gear and Its Application

This video presents a microfluidic phenomenon called “Virtual Vortex Gear (VVG)” and an application of it. The video contains 4 parts and is described as follows: The 1st part shows an application of VVG as a controllable valve in a micro fluidic system and the on and off of the valve are controlled by different flow speeds. The valve is turned on when the flow speed is high enough, and vice versa. The 2nd part shows the generation of VVG and its mechanism. When the flow speed, which is proportional to Reynolds Number, is gradually increased, the flow pattern evolves in the order as (1)parallel streamlines, (2)one vortex, (3)two vortices and eventually (4)three vortices including the last vortex inside the circular chamber. The evolution indicates the transmission of flow energy from the main stream to the inside of the chamber when the flow speed is over a certain range. In addition, every two adjacent vortices rotate in opposite directions which is just like a set of gears, and that is why we named it “VVG”. In the 3rd part, an application of VVG for chemical injection is demonstrated. A colored liquid is represented for the chemical and is surrounded by different sheath flow for the control of injection locations. It is found that only the fluid in a particular pinpoint can be injected into the target chamber. Furthermore, the complex but stable 3D flow patterns are visualized from the video. The last part of the video shows that different amount of chemical injection can be performed in different chambers along the same main stream and the distribution of the color is gradually become uniform by spontaneous diffusing.