Uniform Microsphere Formation by Liquid Choppers Utilizing PZT Actuator: Theoretical and Simulation Study

An innovative uniform microsphere formation based on MEMS was developed by numerical simulation as a preliminary study. This simulation study proposes a new technology to cut off a hydrodynamically focused liquid filament into micro-sized spheres applying a novel combination of hydrodynamic flow focusing and an oscillating external flux. A dispersed phase flow is surrounded by an annular continuous phase sheath flow at upper stream of the main channel on a microchannel module. The focused liquid filament is driven to lower of the channel and cut by fluctuating flux from external channels. The oscillation of the external flow is generated by a piezoelectric actuator that deforms with a frequency yielding high pressure on the stream of the main channel. The initiated high pressure of the external flow overcomes the interfacing forces of the two-phase flows, and the focused liquid filament is pinched off, which is characterized as a liquid chopper. This liquid chopper is activated in various frequencies and pressures generating different sizes of uniform microspheres. The simulation results explain that the size of the microspheres is well controllable by the piezoelectric actuator. This proposed novel method promises high potential to produce various sizes of microspheres without additional changes of the geometry of the microchannel.