Time-dependence of the adhesion of micrometer-size particles to substrates: Correlation with postdeposition particle rotation

The time dependence of the detachment force of 7-mu m ground polyester particles coated with silica nanoparticles from a ceramer-coated substrate was determined by ultracentrifugation. The detachment force of the particles from the substrate was found to increase with the time since the particle deposition. Scanning electron microscopy (SEM) results show that, following deposition, the particles rotate at approximately the same scale as the observed increase in the detachment force. This suggests that the increase in adhesion may be due to particle rotation from their initial positions obtained upon deposition to a more stable position that results from torques generated by either electrostatic or van der Waals forces acting on the particles.