The Interfacial Physics Group

Abstract

Wetting on ambient surfaces is history dependent. The macroscopic manifestation of this history dependence is contact angle hysteresis. The hysteresis arises from the chemical and physical heterogeneity of these surfaces. Accompanying this macroscopic phenomenon is unsteady motion of the contact line as it traverses the heterogeneous surface. In fact, this unsteady motion provides the dissipation innate to the hysteretic process.

The emphasis of this thesis has been to develop a logical and feasible way of studying the unsteady contact line motion on heterogeneous, ambient surfaces. Unsteady motion of the contact line has been tracked and characterized. Important lengths and times in the problem have been identified. Our results substatiate models of the metastable states which trap the system, and a common misconception concerning the irreproducible nature of the contact line motion on such surfaces has been dispelled. For the first time the role played by noise in the problem has been unambiguously identified. Our microscopic investigation places the measurement of macroscopic contact angle hysteresis on a firmer footing.