Model and Experimental Study of Surfactant Solutions and Pure Liquids Contact Angles on Complex Surfaces - Drops and Bubbles in Contact with Solid Surfaces - page 185

(a) (b)

(c) (d)

(e) (f)

Figure 2. Surface plots of predicted contact angle for penetrated (Wenzel) wetting (a), (c) (using
Eq. (10b)) and unpenetrated (Cassie) wetting (b), (d) (using Eq. (10e)) on rough surfaces (variable r
and f ) for various surfactant concentrations. Figure 2a, b and c, d correspond to intrinsic water contact
angles of 120 ◦ and 105 ◦ , respectively, with adsorption coefficients held constant at those for SDS on
Teflon AF. It is likely that the solid-liquid adsorption parameters would change on a surface with
intrinsic contact angle of 105 ◦ compared to 120 ◦ . As such, Figure 2c, d should be seen as describing
general trends. Subplots 'e' and 'f' are for two material smooth heterogeneous surfaces for which
θ y | 1 = 70 ◦ (with no autophobic effect), and θ y = 0 ◦ (with an autophobic effect present).

rough surfaces with topological parameters varying from r 0-1,

and intrinsic water contact angle varying from 120 ◦ to 105 ◦ (applying the adsorp-
tion constants for the SDS-Teflon AF system irrespective of intrinsic water contact

= 1-5 and f =