Gating valve on spinning microfluidic platforms: A flow switch/control concept

Flow switching on spinning microfluidic platforms, i.e., usually based on Coriolis force enables more sophisticated and flexible assay sequences such as mixing, metering, preparation and manipulation of high quality DNA and so on. Thus far flow switching techniques on centrifugal microfluidic platforms have been accomplished by changing the spinning direction or by exploiting external power sources, e.g., pneumatic or thermo pneumatic pressure. We have devised a gating microstructure that controls the flow direction in centrifugal microfluidics without the need of changing the direction of the disc rotation, applying surface treatments or employing external sources. The device is a frequency dependent valve that is able to direct the flow to one direction (e.g., cw) at low frequency and to the opposite direction (e.g., ccw) at higher frequencies. At low frequencies the liquid follows a micropath as a consequence of the specific gating microstructure and at higher frequencies liquid follows the direction of the Coriolis force. The flow behavior of the new valve for di water as well as liquids with different physicochemical properties has been investigated experimentally and numerically. The results show that the new valve is able to control the flow direction on spinning microfluidic platforms for liquids of the wide range of physicochemical properties.