Understanding Nanoparticle Diffusion and Exploring Interfacial Nanorheology Using Molecular Dynamics Simulations

We have studied the dynamics of nanoparticles at polydimethylsiloxane (PDMS) oil-water interfaces using molecular dynamics (MD) simulations. The diffusion of nanoparticles in pure water and low viscosity PDMS oil are found to be reasonably consistent with the prediction by the Stokes-Einstein equation. In addition, we have calculated the shear moduli and viscosities of bulk oil and water as well as oil-water interfaces from single-nanoparticle tracking and demonstrated the potential of probing nanorheology from a MD simulation approach. Surprisingly, we found that the lateral diffusion of nanoparticles as well as apparent interfacial nanorheology at the PDMS oil (low viscosity)-water interface are independent of the position of the nanoparticle at the interface.