Development and parametric analysis of the resonant micro fan for fluidic transport and suspended particle collection

The advancement of fluidic microsystem technology relies heavily on the development of compact and reliable fluidic actuators for sample transport and suspended particle collection. The resonant micro fan is well suited for these tasks and can easily be integrated with existing microsystem fabrication processes. The development of the micro fan involved the design of torsionally supported fan plates that were fabricated using polysilicon surface micromachining and flip-chip assembly. To produce flow, the fan plates were induced into resonant deflection through electrostatic actuation. Modeling tools were developed to predict resonant frequency, actuation voltage, deflection mode, and pumping efficiency. A theoretical fluidic analysis was also performed in order to better understand the mechanisms used by the fan to create thrust and collect suspended particles. A complex potential flow model of the vortices assumed to be shed by the micro fan was developed and used to predict a linear relationship between flow production and fan length, deflection and resonant frequency. These relationships were then experimentally validated using parametric arrays designed with the electromechanical modeling tools. The fluidic response of the micro fan was visualized using laser illuminated smoke particles suspended in air. Flow rates of several micro liters per minute were produced by a single micro fan in a rectangular test channel of height 0.8 mm, width 1.2 mm and length 8 mm. Much larger flow rates, up to 1500 μl/min were demonstrated using a series array of 56 fans. Applications for suspended particle collection and transport were demonstrated by micro fans with circular edge profiles. The micro fan was also shown to produce fluidic transport and particle collection in water environments with suspended one micron polystyrene spheres.