Finally,the durability ofthe hierarchically rough coatings (siloxane
+ 2% w/w SiO2) over a wide range of pH is demonstrated in
Fig. 6. For comparison, results collected on silk treated with pure
siloxane are included in Fig. 6. Both surfaces maintain their wetting
properties over the pH range except for extreme basic conditions
(pH = 13.79) where a slight decrease in s is observed. Superhydrophobicity
is maintained in the composite (siloxane + 2% w/w
SiO2) coating because the siloxane material exhibits a good stability
over pH.