The adhesion of spherical particles: Contributions of van der Waals and electrostatic interactions

The forces needed to detach monodisperse spherical polystyrene particles having radii between approximately 1 mum and 6 mum from a polyester substrate were determined using electrostatic detachment. It was found that the removal force varied linearly with particle radius, as predicted by the JKR theory (K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Soc. London, Ser. A 324, 301 (1971)). In addition, the work of adhesion, estimated from JKR theory, was found to be approximately 0.01 J/m(2). This is a reasonable value for a system such as this. These results are, however, inconsistent with the predictions of models that assume that particle adhesion is dominated by electrostatic forces due to either a uniform charge distribution over the surface of the particle or localized charged patches.