ABSTRACT
The determination of contact line tension (CLT) of a solid-liquid-vapour system is a problem, which is not easy to be solved. The controversial discussion about the contact line tension r in the last years corroborates this fact. Due to its very small value - theory predicts r be on the order of some KT11 to KT10 J/m [1-5] - quantitative measurements are difficult and a large scatter in experimental values was obtained, ranging from 10-12 J/m to KT5 J/m [6-10]. The main reason is probably the limited resolution of the microscopy techniques used. A characteris tic length scale for the influence of the CLT, r, can be estimated by relating a typical value expected for r to a typical interface tension o, which yields
10"1' J/m t /ct = — : ----------------r = 1 nm. In other words, a measureable influence of the CLT is to
10“2 J/m2 be expected in the nanometer range, while on larger scales, interfacial tension will dominate the system. Consequently, inherent to low resolution techniques such as optical microscopy there is considerable coarse graining resulting in an ‘effective’
CLT, which may be largely determined, e.g., by the interplay between interfacial tension and nanoscale substrate inhomogeneity. With this hypothesis it is reason able to follow the concept of preparation and investigation of nanoscale liquid structures to determine exact values of CLT.
