Macroscopic graphene structures such as graphene papers and fibres can be manufactured from individual two-dimensional graphene oxide sheets by a fluidics-enabled assembling process. However, achieving high thermal-mechanical and electrical properties is still challenging due to non-optimized microstructures and morphology. Here, we report graphene structures with tunable graphene sheet alignment and orientation, obtained via microfluidic design, enabling strong size and geometry confinements and control over flow patterns. Thin flat channels can be used to fabricate macroscopic graphene structures with perfectly stacked sheets that exhibit superior thermal and electrical conductivities and improved mechanical strength. We attribute the observed shape and size confinements to the flat distribution of shear stress from the anisotropic microchannel walls and the enhanced shear thinning degree of large graphene oxide sheets in solution. Elongational and step expansion flows are created to produce large-scale graphene tubes and rods with horizontally and perpendicularly aligned graphene sheets by tuning the elongational and extensional shear rates, respectively.

宏观的石墨烯结构，例如石墨烯纸和纤维，可以通过流控组装工艺从单个二维氧化石墨烯片制造。然而，由于未优化的微观结构和形态，实现高的热机械和电性能仍然具有挑战性。在这里，我们报告了通过微流体设计获得的具有可调石墨烯片排列和方向的石墨烯结构，从而实现了强大的尺寸和几何形状限制以及对流型的控制。薄的扁平通道可用于制造具有完美堆叠片材的宏观石墨烯结构，该片材具有优异的导热性和导电性，并提高了机械强度。我们将观察到的形状和尺寸限制归因于各向异性微通道壁的剪切应力的平面分布以及溶液中大型氧化石墨烯片增强的剪切稀化度。通过分别调节伸长率和伸长率的剪切速率，产生伸长和阶梯膨胀流，以生产具有水平和垂直排列的石墨烯片的大规模石墨烯管和棒。