(353f) Transport and Dispersion in Segmented Gas-Liquid Flow through a Forest of Micropillars

Günther, A., University of Toronto
Jensen, K. F., Massachusetts Institute of Technology

Fluid interfaces provide unique opportunities for micro and nanofluidic systems. Capillary numbers of the considered surface-tension dominated flows are generally smaller than 0.01 and the flows display a rich dynamic behavior, provide large interfacial areas and enhance scalar transport by creating secondary flows. These advantages allow, e.g., the controlled facilitation of highly exothermic gas-liquid and fluid-solid reactions in microchemical systems.

We discuss the interaction of multiphase flow with a 1000um wide, 150um deep and 700mm long microchannel network that is soft-lithographically patterned and populated with a regular forest of microfabricated pillars (diameter: 50um-100um, see Figures a,b). Our studies connect to fundamental work on flow in porous media and has applications in chromatography and catalysis. Gas-liquid flow patterns between pillars and their dynamics are determined in pulse-laser fluorescent micrographs and with microscale particle image velocimetry measurements. The presence of persistent static fractions, mixing and axial dispersion are compared with multiphase flow through macroscopic structured/unstructured beds and porous media.

A piezo-electric sample-injector [1,2] is integrated into the chip (c) and allows to inject 100nl tracer volumes and integrated spectroscopy is used to determine axial dispersion from the broadening tracer pulse. Pulse-laser fluorescence microscopy reveals multiphase flow patterns (d). Dispersion is significantly reduced influenced in comparison to single-phase flows and the separation of nanoparticles based on size exclusion in thin liquid films is demonstrated.


[1] Guenther, A., Khan, S.A., Trachsel, F., Thalmann, M., Jensen, K.F. Lab on a Chip, 4 (4), 2004.

[2] Trachsel, F., Guenther, A., Khan, S.A., Jensen, K.F. Chem. Eng. Sci., 60 (21), 2005.