In transport phenomena involving colloidal nanoparticle (NP) suspensions in complex environments, the inter particle interactions play an important role especially when the sizes of the confining environments approaches the particle sizes. Specific examples of such systems are encountered in NP transport through nanochannels used in drug delivery and nanofluidic cooling[1–5]. In ionic colloidal suspensions like the ones encountered in the above applications, the NPs acquire characteristic surface charges which results in a surface potential and a double layer of co- and counter-ions from the solution. DLVO theory predicts the interaction energy resulting from the double layer to be [6]:
Wr=64πkBTRργ2κ2expr
(1)
where r is the separation between NP surfaces, and R is the radius of the NP, ρ is the concentration of ions in the suspension, κ−1 is the Debye screening length (characteristic size of the double layer) and kB and T are the Boltzmann constant and the temperature. As κ−1 approaches the size range of the particles, the interactions amongst the particles may span several times the particle size and contributes to particle diffusion.
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