Contact Angle Measurements over Macro, Micro and Nano Dimensioned Systems - Drops and Bubbles in Contact with Solid Surfaces - page 9

(A) (B)

(C)

Figure 2. Microscopic vs. nanoscopic comparison of a natural and mechanically polished metal sur-
face.

reformulation of this Theory followed by a best fit approach able to determine the
acid-base parameters of both liquid and solid without any further information on
materials involved in the experimental activity.

F. Experimental Application

Apart of mica [(KAl 2 Si 3 AlO 10 (OH) 2 ] and silicon wafers for electronic application
most of the materials cannot be considered as 'flat and homogeneous' as they may
eventually look in a macroscopic analysis. When macroscopic (centimetric) wide
droplets lie on a surface different from a clearly rough one the problem of the real
surface morphology seems far away. When, on the other hand, we deal with mi-
cro/nanoscopic drops or, even easier, we focus our attention to the triple line , i.e.,
the visible perimeter contour between solid surface-liquid-environmental fluid, the
morphology topic turns up.
Figure 2 illustrates the problem as it may show up for a bulk metal surface
(molybdenum in this case). At a first macroscopic insight the substrate sample
was originally looking flat but on a microscopic analysis (Fig. 2A) several bumps
and defects were found emerging by the surface. After a normal smoothing treat-
ment (Fig. 2B) the surface appeared to be bump free but evident regular scratches