Flow-Regime-Controlled Fabrication of Vertically-Aligned 2D-Nanosheet Fibers
This research reveals that expansion flow generates nanosheet alignment, whereas subsequent plug flow suppresses shear-induced reorientation and preserves the vertically aligned structure. COMSOL Multiphysics was employed to investigate the flow behavior of non-Newtonian graphene oxide (GO) dispersions in an expansion spinneret. By coupling experimentally measured rheological properties with computational fluid dynamics, the evolution of velocity and shear-rate fields was analyzed under different crosslinker concentrations. As shown in Figure 1，the simulations reveal a sequential expansion-flow-to-plug-flow transition at high viscosity: expansion flow drives nanosheet rotation, while the low-shear plug-flow region preserves the generated vertical alignment. In contrast, low-viscosity dispersions develop laminar flow with pronounced velocity gradients, resulting in shear-induced structural disruption. The flow dynamics of 2D material dispersions in an expansion channel were investigated using the Laminar Flow module in COMSOL Multiphysics 6.2. The rheological properties of the dispersion employed in the simulation were determined by fitting the viscosity-shear rate curve . To ensure simulation accuracy, the geometric model was discretized using a free triangular mesh, with additional boundary layer meshing applied to boundary layer regions. The governing fluid dynamics equation is expressed as:ρ(u·∇)u = ∇·[-pI+K]+F. where ρ denotes fluid density, u represents the fluid velocity vector, I is the unit tensor, K corresponds to the volumetric viscous coefficient tensor of the fluid, F denotes the external force vector acting on the fluid, and p indicates fluid pressure.
