Modeling chemical reactions in immiscible fluids in microchannels Presentation (windows Only) & PDF file Local control of periodic pattern formation in driven binary immiscible fluid Presentation (windows Only) & PDF file
Binary Fluid within the Microchannels: Morphological instabilities and periodic droplet formation.
What happens if we drive two parallel fluid streams, A (in blue) and B (in yellow) through the patterned microchannel?
Patches on the top and on the bottom substrates are in registry and form a “checkerboard”. In the first set of patches, A-like (B-like) stripe that preferentially attracts A (B) component is placed on the way of B(A) fluid stream, in the second set of patches, A-like and B-like stripes are reversed.
We found that the system bifurcates between time-independent behavior and different types of regular, non-decaying oscillations in the structural characteristics that give rise to the periodic formation of B-in-A droplets near the front wall and, simultaneously, A-in-B droplets near the back wall. The surprisingly complex behavior is observed even in the absence of hydrodynamic interactions.
Here are examples of two types of oscillations:
H=0.00028; time range t =55000 to t=73000 (60 snapshots)
H=0.00032; time range t =55000 to t=73000 (60 snapshots)
For details, see:
Olga Kuksenok, David Jasnow, Julia Yeomans, and Anna C. Balazs. Periodic Droplet Formation in Chemically Patterned Microchannels, Phys. Rev. Lett. 91, 108303 (2003).
PDF file - 525 KB
Patches on the top and on the bottom substrates consist of two stripes only; A-like (B-like) stripe is places on the way of B(A) fluid stream.
Complex structure, where A and B phase are intertwined, forms in the center of the channel and decays close to sidewalls. This structure is periodic in space (along the flow direction) and in time.
In order to see the structure, we cut the channel by vertical plane near the center and made the front part of the channel transparent (movie on the left). Movie on the right shows the morphology at the outlet of the channel.
For details, see:
Olga Kuksenok, David Jasnow, Anna C.Balazs. Diffusive Intertwining of Two Fluid Phases in Chemically Patterned Microchannels (Phys. Rev. E (2003), in press)
Olga Kuksenok and Anna C.Balazs. Harnessing Chemical Patterning to Direct the Flow of Binary Fluids in Microchannels (submitted).