Wetting Dynamics of Aqueous Surfactant Solutions on Polymer Surfaces - Drops and Bubbles in Contact with Solid Surfaces - page 77

(a) (b)

(c) (d)

Figure 8. An optical image of a plain fabric surface (a); schematic of a complex fabric structure: the
total profile contains both roughness and waviness information (b); filtered roughness profile of a plain
fabric surface as an example (c); filtered waviness profile of a plain fabric surface as an example (d).
Reprinted from Textile Research Journal 78, Hasan M. M. B., Calvimontes A., Synytska A., Dutschk V.,
pp. 996-1003, Copyright (2008) , with permission from SAGE publications.

according to Extrand and Kumagai [10]. A textured solid can be considered as a
two-dimensional porous material in which liquid can be absorbed by surface wick-
ing [11]. This wetting regime is intermediate between spreading and imbibitions.
When the contact angle is smaller than a critical value θ cr , a film propagates from
a deposited droplet, a small amount of liquid is sucked into the texture and remain-
ing drop sits on a patchwork of a solid and liquid. It is very common that fibrous
materials encounter roughness on surfaces and walls of pores. The driving force for
such surface wicking depends on the geometry of the grooves, the surface tension
of the liquid and the free-energies of the solid-gas and solid-liquid interfaces. An
excellent overview on different wetting regimes for rough surfaces is given in [12].
New topographic concepts for a mechanistic understanding of wetting phenom-
ena were presented by the authors in [13-16]. Moreover, in [17] was shown that
there are significant differences between the soiling behaviour and cleanability of
polyester textile materials with different topographic structures despite the similar-
ity of their chemical nature. Toward a better mechanistic understanding soil removal