A Study on Surface Force Measurement for Contacted Arbitral Two Surfaces —Effect of Surface Roughness, and Indirect Surface Force Measurement Method

The present paper is intended to show effect of surface roughness on surface force measurement and to demonstrate a newly-proposed indirect surface force measurement using two probes. In the case of hydrogen-terminated and octadecyl-trichloro-silane-coated Si surfaces with micro-mounds, measured surface forces is strongly affected by micro-roughness. The surface force, which varies from 2 μN to 180 μN, is proportional to the logarithm of the curvature radius of the micro-mound. Meanwhile, in the proposed indirect measurement method of surface force, surface force of arbitrary two surface is calculated on the basis of modified JKR and Fowkes theories with surface forces measured by two kinds of probes. The authors prepared a specialized OTS-coated probe as well as a standard glass probe to verify validity of the indirect surface force measurement. For a case of surface force between Si and APTES surfaces, the indirectly measured value reasonably corresponds to the directly measured value. It is confirmed that the proposed method is effective for surface force evaluation for arbitrary two surfaces without probe coating.