THE ROLE OF SURFACE-ROUGHNESS AND CONTACT DEFORMATION ON THE HYDRODYNAMIC DETACHMENT OF PARTICLES FROM SURFACES

The effects of elastic deformation and surface roughness on the hydrod ynamic detachment of colloidal particles from surfaces have been studi ed. Experimental results for glass and polystyrene particles on glass and mica substrates are reported. A theoretical model is developed usi ng a Green's function formulation to ex plain the origin of the restra ining torque acting on the particle Two limiting situations are analyz ed: (a) rigid sphere on a deformable substrate and, (b) deformable sph ere on a rigid substrate. It is concluded that surface roughness is a necessary condition to account for the observed critical hydrodynamic force. The magnitude of this critical force has been found to depend o n three competing factors: particle roughness, roughness of the substr ate, and the extent of contact deformation. (C) 1994 Academic Press, I nc.