(204c) Adhesion Force of Glass Particle on Silica Surface with Periodic Roughness Structure in Humid Atmosphere

Adhesion force between solid surfaces is one of the fundamental properties for surface control. In the atmosphere, especially, the adhesion force between particles depends on the relative humidity; while such dependencies have been reported by many researchers, no consistent view is available among them. In this paper, using an atomic force microscope (AFM), adhesion forces between glass particles or AFM tips and a silica plate with periodic roughness structure were measured as a function of relative humidity, in order to get better understanding at microscopic level. To clear the effect of van der Waals force on the rough surface, the forces were measured at less than 10 % relative humidity. The observed adhesion force with periodic roughness structure was very weak comparing with that with smooth surface. The van der Waals force between a particle and a plate with smooth surface is proportional to the particle diameter, but the observed force with periodic roughness structure was not in proportion to the particle diameter. This observed adhesion force can be estimated by the calculation of van der Waals force with numerical integration method considering the periodic roughness structure of the silica surface. As increasing relative humidity, the observed adhesion forces between the glass particle and the silica plate with periodic roughness structure increased gradually from that measured at less than 10 % relative humidity, but these values were very smaller than the adhesion forces with smooth surface as the relative humidity was equal. This concludes that a capillary force or a liquid cross-link force does not affect to the adhesion force with rough surface, even at the high humid condition.