It is the objective of this thesis to describe how micro-patterned polymeric surfaces can lead to enhanced transport through and along those surfaces. The main focus is on increasing the flux in membrane processes. For gas permeation, micro-lines in a dense polymer can increase the mass transport compared to flat membranes with the same polymer volume. Finite element simulations prove that the pattern facilitates lateral diffusion paths, which lead to experimental flux enhance-ments up to 59%. To study the liquid-solid interaction on a hydrophobic micro-patterned surface, several fundamental questions are investigated. How (fast) does the liquid flow between micro-pillars during the Cassie-Baxter to Wenzel transition? A high-speed camera has captured from below the dynamics of the liquid flowing between different micro-pillar arrays (PDMS and Kra-ton). The front velocity of the liquid increases with increasing gap size and decreasing hydropho-bicity and pillar height. Lattice Boltzmann simulations have confirmed these results and gener-ated 2D and 3D flow profiles. This generated the question: can we scale the experimental results to predict the liquid velocity? Several scaling arguments were derived from a macroscopic energy balance between two pillars and tested against the experimental results. A third question on the liquid-solid interaction is raised: how will hydrodynamic slip effects above micro-lines influence membrane performance? Velocity profiles above dense PDMS and porous PVDF were measured experimentally and compared with an analytical approach to determine the effect of slip on con-centration polarization layers. The boundary layer thickness can be decreased by a factor 2 through slip. The obtained knowledge of gas/liquid – micro-pattern interaction can be of use in a wide range of research fields and industries.
|Award date||9 Jan 2009|
|Place of Publication||Enschede|
|Publication status||Published - 9 Jan 2008|