Moving contact lines and Langmuir-Blodgett film deposition

The objective of this paper is to point out the close relationship between contact line dynamics and LB film depositions, and it is designed to serve as a blueprint for future analysis of the LB technique. Moving contact lines and contact angles play a major role in Langmuir-Blodgett ultrathin film depositions. Although the effect of contact angles has been recognized for many years, a fundamental and comprehensive explanation of the phenomena taking place at the contact line has not been formulated before. Our understanding of contact line dynamics has improved thanks to careful experiments and new theoretical developments. Flow patterns depend on dynamic contact angle and the ratio of viscosities of the gas and liquid phases. More recently dynamic contact angles-and flow patterns-have been linked to forces of molecular and double-layer origin. The dynamic relationship of flow patterns to interfacial and transport properties can be used to explain seemingly contradictory experimental results reported by researchers during more than 60 years of experience with the L-B technique. Windows of operability can be defined for X-type and Z-type depositions that are useful in the design of experimental and industrial L-B deposition equipment.