On the Sliding down of Liquid Drops on Inclined Plates (2nd Report, Sliding Angles on SAMs Surfaces)

Abstract

The sliding angle of liquid drops on inclined plates were investigated in order to evaluate the characteristics of SAMs (Self-Assembled Monolayers) surfaces. The contact angles and sliding angles for two kinds of test liquids, i.e., BCA and Ethylene glycol, were measured on 4 kinds of SAMs surfaces made by the immersion method with different immersion times. The contact angle hysteresis became minimum on the standard film, i.e., the most homogeneous surface. The experimental sliding angles φ agreed well with the theory discussed in the preceding report. Using the small drop (1μL), the difference of φ between the standard film and others could be made larger than that of the contact angle hysteresis. The film characteristics can be evaluated from rather simple measurement of sliding angles. The 3-dimensional drop profile on the inclined plate was discussed from an approximate theory. Assuming circle and ellipse as the attached surface profile, the drop configuration was calculated from the approximate Laplace equation. The results agreed well with the experimental profiles.