PZT actuator-controlled high-frequency microdroplet generation: Reducing the restrictions of channel size, fluid viscosity, and flow rate

Abstract

For passive generation of microdroplets, the droplet volume correlates with the flow rate and the generation frequency, and is further influenced by the channel size and fluid viscosity. To improve the control flexibility, we study the active droplet generation using a cost-effective piezo disk actuator. In this method, the droplet generation frequency is synchronized with, and hence can be directly set by, the piezo actuation. Both the flow rates of the discrete and continuous fluids can be independently controlled, leading to linear tunability of the droplet volume and spacing. The restrictions of the channel size and fluid viscosity are also reduced. Furthermore, this is achieved at high frequencies up to several thousand Hertz, and at reduced continuous-fluid/discrete-fluid flow rate ratios. Using the same method, flexible modulation on the size and morphology of double-emulsion microdroplets is also demonstrated.