Application of probe rheology simulation technique in rheological characterization of soft matter

The relation between the motion of an embedded small spherical particle in a fluidic medium and the mechanical properties of the medium was first established through the pioneering work of Einstein, Sutherland, and Smoluchowski and Langevin. With the advent of particle tracking techniques, the practice of extracting the viscoelastic moduli of the soft matter from either the thermal or forced motion of a probe particle was established and further developed into an experimental technique known as Microrheology. More recently, a simulation technique analog to the Microrheology procedure, known as the Probe Rheology Simulation Technique (PRST), has been developed in our research group. A modification to PRST formalism to account for the slip at the probe particle surface is presented in the first part. Next, PRST is used to calculate the viscosity of water, and the effect of the slip, the satisfaction of the continuum approximation, and the performance of the method compared to other conventional simulation techniques for viscosity calculation are discussed. Moreover, a procedure for selecting the simulation parameter for the PRST in active mode is considered, and a set of criteria for the successful application of PRST in active mode are presented. Finally, a band-pass filter for limiting the noise in the stress data obtained from Non-Equilibrium Molecular Dynamics simulations at lower frequencies is designed. A method for addressing the artificial hydrodynamic interactions, which has previously been applied to a weakly entangled polymer melt, is presented. PRST in conjunction with the aforementioned method and the NEMD simulations augmented by the band-pass filtered are utilized for the low-frequency characterization of a heavily entangled polymer melt.