Passive control of two merging streams for microfluidic devices

This paper describes the pure passive scheme that manipulates the multiple streams using microfluidic device. This device relies on capillarity to control merging of two streams and to regulate the volumetric flow rate (VFR). This sophisticated manipulation of the capillarity is, however, nontrivial due to the lack of the passive and precise means. Here, we control the capillarity precisely and rapidly through the geometry of the junction of two streams and the hydrophilicity of the substrate. Additionally, we use the relative flow resistance to control the VFR ratio of the merged two streams. This passive scheme leads to the significant simplification of the control of the multistream without sacrificing the rapidity and precision. When combined with the microfluidic components such as mixers, reaction chambers, and detectors, this passive scheme offer the possibility of designing disposable and integrated microfluidic systems.