How do chemically or topographically patterned walls influence the flow field and hydrodynamic resistance in a microchannel?
HYDRODYNAMIC RESISTANCE IN MICROCHANNELS WITH CHEMICALLY OR TOPOGRAPHICALLY PATTERNED WALLS
Supervisors: Riëlle de Ruiter and Frieder Mugele
The behavior of single- and two-phase flows in confined geometries has been subject of investigation due to its wide-range implications, including microfluidic devices as well as oil recovery in porous media. The two-phase flow of oil and water through porous rock can be modeled by the flow of a droplet through a liquid-filled microchannel.
The presence of both wall heterogeneities and drops alters the flow field in a microchannel, and changes the hydrodynamic resistance of the channel. Recently, a microfluidic comparator [1-3] has been developed (Figure 1). The displacement of the interface in the comparator region yields information about the hydrodynamic resistance and pressure drop in rectangular microchannels.
Fig. 1 (A) Schematic diagram of the T-junction device integrated with a microfluidic comparator. (B) Interface displacement (DY) is zero, when equal driving pressures are imposed at the inlets of the oil phases. (C) Interface moving upwards during the pinch-off process. (D) Interface moving downwards during the advection of a drop. Scale bar is 200 mm and is the same for (B), (C), and (D).
The central questions of the project is: How do chemically or topographically patterned walls influence the flow field and hydrodynamic resistance in a microchannel?
Two different subjects are available:
(1) Chemically patterned walls: using microcontact printing techniques, patterns of self-assembled monolayers are formed onto planar surfaces using relief stamps. In this way, we can create surfaces with patches of variable wettability.
(2) Topographically patterned walls: using soft-lithography, topographically patterned surfaces are produced. Examples of such surfaces are superhydrophobic surfaces, or walls with grooves or constrictions.
The comparator is reversibly sealed to a patterned surface (modular microfluidics) to determine the hydrodynamic resistance of the thus closed channel in case of single- and two-phase flows.
This project involves soft lithography to produce the comparator, (1) microcontact printing to chemically pattern surfaces or (2) production of topographically structured surfaces, microscopy, high speed imaging and subsequent image analysis, and possibly particle image velocimetry.
If you would like to have more information about this thesis assignment, please contact Riëlle de Ruiter (firstname.lastname@example.org) or Frieder Mugele (email@example.com).
 M. Abkarian et al., PNAS 103, 538-542 (2006)
 S.A. Vanapalli et al., Applied Physics Letters 90, 114109 (2007)
 S.A. Vanapalli et al., Lab on a Chip 9, 982-990 (2009)