Brownian dynamics simulation of two‐dimensional nanosheets under biaxial extensional flow

Abstract

The morphology dynamics of two-dimensional nanosheets under extensional flow are investigated using a coarse-grained model. Nanosheets (graphene, BNNS, MX 2 ) are promising materials for a variety of materials and electronics applications. Extensional flow fields are often present during dispersion processing, such as spin coating. Both nanosheet properties (e.g., moduli, size) and processing parameters (e.g., extension rate) can have a significant impact on the nanosheet morphology and thus, the structure and properties of the bulk material. Our previously developed dimensionless Brownian dynamics methodology is used to explore biaxial extensional flow. Nanosheets exhibit a flat conformation under extensional flow for high bending moduli and an extended "washrag" conformation for low bending moduli. Intrinsic extensional viscosity increases with strain before reaching a plateau. The intrinsic viscosity exhibits a weak power law with nanosheet molecular weight. These simulation results allow for experimental control over morphology as a function of nanosheet properties and flow type and strength.

Buckling, crumpling, and tumbling of semiflexible sheets in simple shear flow

“…Relatively less work, though, has focused on the behavior of 2D semiflexible sheets in low-Reynoldsnumber flows, despite the increasing relevance of transition metal dichalogenides, graphene 22 , graphene oxide 23,24 , and 2D polymers 25,26 in advanced technologies. Xu and Green 27,28 looked at sheets under shear and biaxial extensional flow, and Babu and Stark 29 have studied tethered sheets in fluids, confirming predicted scaling laws of Frey and Nelson 30 regarding thermal fluctuations in the presence of hydrodynamic interactions. Additionally, Dutta and Graham 31 have studied Miura-patterned sheets and observed various interesting dynamical regimes involving periodic tumbling, unfolding, and quasiperiodic limit cycles.…”

Thermally fluctuating, semiflexible sheets in simple shear flow

“…Notable previous works on the subject, though, include the following. Xu and Green 44,45 studied the behavior of sheets under shear and biaxial extension and found slight shear-thinning at large shear strengths. Babu and Stark 46 studied the fluctuations of tethered sheets in fluids via stochastic rotation dynamics, confirming predicted scaling laws of Frey and Nelson 26 (i.e., that the intermediate scattering function exhibits sub-diffusive scaling that reflects the self-similar roughness of the fluctuating surface).…”

Thermally Fluctuating, Semiflexible Sheets in Simple Shear Flow

“…Notable previous works on the subject, though, include the following. Xu and Green [44,45] studied the behavior of sheets under shear and biaxial extension and found slight shear-thinning at large shear strengths.…”