Experimental Study of the Entrainment of Nanoparticles from Surfaces

The adhesion and resuspension of nanoparticles is important in applications ranging from semiconductor manufacturing to pollution management. The objective of this work is to understand the effect of particle size on re-entrainment of nanometer scale particles. One of the major contributions is to reduce the randomness introduced in past measurements on resuspension by controlling humidity, temperature, material and the distribution of shape and particle sizes. In the process of studying particle size, the effect of surface roughness was also found. Measurements of the detachment fraction of carbon particles as a function of flow rate show three distinct regimes that we attribute to the dominance of drag, energy accumulation by particles, and collision and agglomeration respectively. Experiments with silica nanoparticles on silica microspheres show the detachment fraction to increase non-linearly with particle diameter and to decrease with the substrate diameter. We attribute the former to the dominance of the drag moment over the adhesive moment. We attribute the influence of the substrates to the surface roughness being comparable to the size of the nanoparticles. This work provides new empirical insight into the interaction of nanoparticles with surfaces and fluid flows