ABSTRACT
Experiments on Evaporating Thin Films . . . . . . . . . 655
Multicomponent Solvents and
Surface Tension Gradients . . . . . . . . . . . . . . . . . . . 657
Summary: Time Scales . . . . . . . . . . . . . . . . . . . . . . 660
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . 660
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660
Evaporation sets an important time scale for the formation of structure in sol-gel films during dip coating, and
surface tension is the dominant driving force influencing that structure. The action and interplay of these two
phenomena were evaluated by experiments with pure and binary solvents. From the optically measured thick-
ness of the steady-state film profile, accelerated evaporation near the drying line that sets stringent constraints
on the time available for network formation was found. In binary solvents, there is evidence for strong
flows driven by surface tension gradients; this flow gives rise to capillary instabilities. Aided by these flows,
differential evaporation leads to regions rich in the nonvolatile component near the drying line.
