Model and Experimental Study of Surfactant Solutions and Pure Liquids Contact Angles on Complex Surfaces - Drops and Bubbles in Contact with Solid Surfaces - page 203

(a)
(b)
Figure 10. Advancing contact angle on (a) Teflon AF and (b) OTS coated aluminum versus advancing
contact angle on (a) Teflon AF and (b) OTS coated, smooth silicon for pure liquids and surfactant
solutions of similar intrinsic contact angle. Surfactant solutions show generally higher contact angles
than the pure liquids. For the modified Cassie prediction, f is (a) 0.06 and (b) 0.04, the dashed line
shows super CMC concentrations of SDS. In (a), the Teflon AF coated silicon contact angles are
linear interpolations or extrapolations from the closest measured data to match measured values of
concentration/surface tension of surfactant solutions on aluminum to Teflon AF coated silicon. Error
bars show one standard deviation.
F. Closing Remarks
A model has been derived, from first principles, describing the effect of surfactant
adsorption on equilibrium contact angle on complex surfaces (i.e., rough and/or het-
erogeneous) wetting in the Wenzel or Cassie modes. Experimental data for aqueous