Wetting of structured substrates and flexible membranes

Monday, December 7, 2009 - 1:30pm - 2:10pm
EE/CS 3-180
Reinhard Lipowsky (Max Planck Institute for Colloids and Interfaces)
Keywords: Wetting phenomena, surface domains, surface topography,
contact line pinning, fluid membranes, vesicles, intrinsic contact angles

Abstract: Two types of wetting phenomena will be discussed: (i) Morphological wetting
transitions at chemically patterned or topographically structured substrates; and
(ii) Wetting of flexible membranes such as lipid bilayers by aqueous phases.
Morphological wetting transitions between different droplet shapes occur, e.g., as one
varies the amount of liquid deposited on the structured substrate. [1,2] The basic
mechanism underlying this polymorphism is the freedom of contact angles at pinned
contact lines. [3] The second system consists of lipid vesicles containing aqueous
solutions with two species of water-soluble polymers. When the polymer concentrations
are raised by deflation, the aqueous solution forms two coexisting liquid phases that
may undergo complete-to-partial wetting transitions at the vesicle membranes. [4] Partial
wetting is characterized by effective contact angles that can be measured by optical
microscopy and by an intrinsic contact angle that represents a 'hidden' material parameter. [5]

[1] R. Seemann et al. PNAS 102, 1848 (2005)

[2] P. Blecua, M. Brinkmann, R. Lipowsky, and J. Kierfeld. Langmuir (in press)

[3] R. Lipowsky et al. J. Phys.: Condens. Matter 17, S2885 (2005)

[4] Y.-H. Li, R. Lipowsky, and R. Dimova. JACS 130, 12252 (2008)

[5] H. Kusumaatmaja, Y.-H. Li, R. Dimova, and R. Lipowsky. Phys. Rev. Lett. (submitted)

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