The forces needed to remove monodisperse spherical toner particles from an organic photoconductor were determined using electrostatic detachment for a series of particles having diameters between 2 μm and 12 μm. It was found that the removal force varied linearly with particle radius, as predicted by JKR (Johnson, Kendall and Roberts, Ref. 19). This result is inconsistent with the predictions of models that assume that the detachment forces are dominated by either a uniform charge distribution over the surface of the particle or localized charged patches. Moreover, reasonable works of adhesion are obtained if one assumes that the removal forces are dominated by surface, rather than electrostatic, forces. These results seem to suggest that, for spherical toner particles in this size range, adhesion may be dominated by van der Waals interactions.
D. S. Rimai, D. J. Quesnel, L. P. DeMejo, M. T. Regan, "Toner to Photoconductor Adhesion" in Journal of Imaging Science and Technology, 2001, pp 179 - 186, https://doi.org/10.2352/J.ImagingSci.Technol.2001.45.2.art00010