Applications of Micro-Electro-Mechanical Systems (MEMS) have become sophisticated and extensive recently. As the microsystems, such as biomedical and chemical analytic devices, are broadly developing, understanding of flow behavior in fluidic microdevices is vital in order to devise efficient and economic microsystems. The advanced micromaching technologies available for fabrication are the best tools to explore the governing mechanism of this little-known flow phenomena in the miniature passages. Unexpected activities, like separation or mixing in flow with very small reduced Reynolds number, in microchannels with complex microstructures are important and cannot be neglected. Hence, two kinds of these devices were studied....[ Read more ]

Applications of Micro-Electro-Mechanical Systems (MEMS) have become sophisticated and extensive recently. As the microsystems, such as biomedical and chemical analytic devices, are broadly developing, understanding of flow behavior in fluidic microdevices is vital in order to devise efficient and economic microsystems. The advanced micromaching technologies available for fabrication are the best tools to explore the governing mechanism of this little-known flow phenomena in the miniature passages. Unexpected activities, like separation or mixing in flow with very small reduced Reynolds number, in microchannels with complex microstructures are important and cannot be neglected. Hence, two kinds of these devices were studied.

Bends or curves are inevitable components in fluidic systems and always induce secondary flows. A set of microchannels, 20μmx1μmx5810μm nominal dimensions, integrated with pressure microsensors, with a 90°-turn at the center were fabricated to investigate this flow field with miter, curved, and double-turn configurations. Gas was passed through the microdevices, and mass flow rate was measured as a function of the driving pressure drop. Pressure distributions along the microchannels were recorded, showing additional pressure drop across the bends. Both the measurements indicate that secondary flow could develop in the microchannels due to the bend.

Merging of microfluidic streams is expected to be another key feature in microsystems. An integrated microdevice consisting of microchannels and pressure microsensors was developed to study this phenomenon. Two narrow, uniform and identical channels merged smoothly into a wide, straight and uniform channel downstream of a splitter plate. Mass flow rates and pressure distributions were measured for single-phase gas flow in order to characterize the device. Flow visualizations of two-phase flows were conducted when driving liquid and gas through the inlet channels. Several instability modes of the gas/liquid interface were developed as a function of the pressure difference between the two streams at the merging location.