ABSTRACT
The key to predicting the adhesion force as a function of surface topography is to model the roughness in a manner that more closely resembles the true geometry of the surfaces. The PERC model was developed through a theoretical analysis of the surface topography measured experimentally using the AFM [11, 12]. The surface topography was described mathematically using both the height and breadth of the asperities, which were expressed as RMS roughness and peak-to-peak distance, X, respectively. The force of adhesion, F, scaled by the particle radius, R, was expressed as:
1 1
+ F ~R 6H* 1 + 58.14/? -RMS X2 lMlRMSV
Ho / _
(1)
where A is the Hamaker constant and H0 is the minimum separation distance (0.3¬ 0.4 nm). The local radius of the surface asperities determined by this method was much larger as compared to the previous models [10, 16]. The PERC model, using a van der Waals force based approach, predicts the force of adhesion within
tftip = 50nm
2 4 6 8 10 RMS surface roughness (nm)
