| Summary: | 博士 === 國立臺灣大學 === 應用力學研究所 === 95 === Abstract
In this study, the results of two unsteady flow microfluidic devices with multifunctions of fluid pumping, mixing and particle removal are presented. This present device was developed by utilizing the microchannel unsteady flow phenomenon, which was due to the oscillation of a PZT membrane. The flow direction can be controlled by the amplitude and the frequency of the driving power on the vibrating membrane. At a driving frequency of 1.0 kHz, the optimum mixing (over 95%) and particle removal efficiency (close to 100%) are observed at the inlet region and the trifurcate zone.
The fabrication process of this device was simple since only one photo mask, one ICP etching step and anodic glass bonding were required. As for the design of valveless micropump, one asymmetric obstacle was used for the flow-directing device instead of the diffuser/nozzle elements used in previous studies. A mixing region with triangular-wave structures and a trifurcate zone with triple outlet channels were integrated with an obstacle-type valveless micropump for the present multifunctional device. Two side inlet channels with an incline angle of 40° were placed on both sides of the center inlet channel. The fluids from the center and the side inlet channels flow through the throat between the obstacle and the side-wall. Two recirculation zones occurred upstream the obstacle to enhance the mixing efficiency.
Downstream the oscillating chamber, the main channel was connected to a trifurcate zone. The flow velocity in the main channel was measured by flow visualization. At the trifurcate zone, two recirculation zones and two vortices were induced on the both sides of the trifurcate zone and upstream the inlet of the center outlet channel due to the unsteady flow. These vortices served as obstacles to increase the flow resistance of the center channel. Based on the rotating direction of these recirculation zones and vortices, the particles were driven towards side outlet channels to achieve the removal effect.
Micro-particle-image-velocimetry (μ-PIV) with external trigger was used to measure the flow characteristics of the inlet region. Streamtrace patterns were obtained at the inlet region in a time period. Image processing was used to count the number of particles and to analyze the removal efficiency. This study indicates that this device fulfills the demands for sample preparing of bio-chemical or bio-medical systems. Moreover, the present device can be applied to μ-or lab-on-achip with integration of biosensors in the future.
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