A special transport mechanism must be designed for the Micro Total Analysis System (μTAS) to move samples and reagents through the system's microchannels for medical and biomedical applications. A bi-directional microfluidic driving system was developed experimentally in this work. For conventional micropumps, however, complicated relationships exist between the pumping mechanisms, the conditions under which the devices operate and the behavior of the multi-component fluids transported in these channels. This pneumatic system is an on-chip planar structure without moving parts and does not require microfabricated heaters or electrodes. The bi-directional driving module combines two individual components for suction and exclusion. The individual components can be combined using a T-shape connection as well as in parallel. The pumping actuation is introduced to the microchannel fabricated in chip by blowing airflows through this device. In this design, pumping is not straightforward induced by the pressure introduced by the air conduit, but based on reliable physics caused by steady airflows. Modular devices with a parallel connection, presented herein, can provide flexible, predictable, and linear control of bi-directional microfluid pumping. The velocity of the working liquid in the microchannel can be adjusted by varying the inlet flow rates for the suction and exclusion components. This work demonstrated the driving system and investigated the influences of the characteristics of the working liquids experimentally. The driving force, both suction and exclusion, for the liquid with the lower viscosity is stronger than those with the higher viscosity. Furthermore, the surface tension plays an important role in the microchannel. The required flow rate at the suction component is quite large due to the strong surface tension of water. For the presented design, no air conduit was employed to connect the servo-system to the driving system, therefore, the packaging difficulty and leakage problem, which may arise in conventional systems, can be eliminated. The feature that the final airflow outlet is fixed in one direction is most advantageous for preventing cross-contamination between the servo-system and the chip. The driving system is, therefore, particularly suited to microdevices for biochemical analysis.
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