Model and Experimental Study of Surfactant Solutions and Pure Liquids Contact Angles on Complex Surfaces - Drops and Bubbles in Contact with Solid Surfaces - page 193

(a)

(b)

Figure 4. Average contact angle of surfactant solutions on (a) Teflon AF coated and (b) OTS coated
smooth silicon wafer (symbols), and the predicted contact angles using Eq. (10a) with constants ob-
tained from data of SDS on Teflon AF (line). The end points of the bars on symbols mark the advancing
(top end) and receding (bottom end) contact angle. Standard deviation of advancing and receding con-
tact angles are less than ∼ 2.6 ◦ The dotted region of the line indicates super CMC concentrations of

SDS.

2. PTFE Surfaces—Surfactant Solutions and Pure Liquids

Figure 5 shows advancing and receding contact angles of surfactant solutions and
pure liquids on plasma etched PTFE, along with model predictions (made using
Eq. (10b) and (10e)) for Wenzel and Cassie mode wetting of surfactants on the