Anisotropic drop morphologies on corrugated surfaces.
Langmuir 24:14 (2008) 7299-7308
Abstract:
The spreading of liquid drops on surfaces corrugated with micrometer-scale parallel grooves is studied both experimentally and numerically. Because of the surface patterning, the typical final drop shape is no longer spherical. The elongation direction can be either parallel or perpendicular to the direction of the grooves, depending on the initial drop conditions. We interpret this result as a consequence of both the anisotropy of the contact line movement over the surface and the difference in the motion of the advancing and receding contact lines. Parallel to the grooves, we find little hysteresis due to the surface patterning and that the average contact angle approximately conforms to Wenzel's law as long as the drop radius is much larger than the typical length scale of the grooves. Perpendicular to the grooves, the contact line can be pinned at the edges of the ridges, leading to large contact angle hysteresis.Lattice Boltzmann simulation techniques for simulating microscopic swimmers
COMPUT PHYS COMMUN 179:1-3 (2008) 159-164
Abstract:
We use two different sub-gridscale lattice Boltzmann methods to simulate the swimming motion of a model swimmer. We systematically characterise the discretisation errors associated with placing a continuous object on a grid, and place limits on how low the Reynolds number needs to be in order to reach the characteristic zero Reynolds number regime. (C) 2008 Elsevier B.V. All rights reserved.Capillary filling in patterned channels.
Phys Rev E Stat Nonlin Soft Matter Phys 77:6 Pt 2 (2008) 067301
Abstract:
We show how the capillary filling of microchannels is affected by posts or ridges on the sides of the channels. Ridges perpendicular to the flow direction introduce contact line pinning, which slows, or sometimes prevents, filling, whereas ridges parallel to the flow provide extra surface that may enhance filling. Patterning the microchannel surface with square posts has little effect on the ability of a channel to fill for equilibrium contact angle theta_{e} less than approximately 30 degrees . For theta_{e} greater than approximately 60 degrees , however, even a small number of posts can pin the advancing liquid front.Shearing active gels close to the isotropic-nematic transition
(2008)