Resuspension of particles from surfaces: Technological, environmental and pharmaceutical aspects

Particles that were previously deposited on the surface of any substrate are resuspended to the surrounding environment due to complex effects. The effectiveness of resuspension depends on the geometry of deposits in the form of mono- or multilayer geometries, material properties of the particle and the substrate and the interaction of particles with external excitations. The particle leaves the substrate or its surrounding neighbors, if the external force exceeds the adhesive/cohesive force. Different types of adhesive forces, such as van der Waals interactions, capillary forces and electrical double layer forces, are considered. The adhesive effects are extended to the cases of deformable bodies with the formation of the surplus of the contact area between the particle and the substrate. Finally, the adhesion of particles to the rough surface of the substrate is considered. The next sections of this paper are devoted to the analysis of the particle detachment process due to its interaction with a. owing gas of different flow properties, including a pulsating jet flow and a developed turbulent flow. The mechanisms of the pull-off forces as well as sliding and rolling effects in the presence of asperities are also presented. Finally, the detachment of particles from the multilayer structures of deposited particles is analyzed. The paper is summarized focusing on the practical aspects of resuspension, including the techniques of cleaning of the wafer surface, environmental consequences of resuspension with health risk and the application of resuspension for the production of inhalable particles from drug powder structures. (c) 2008, The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.