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Microfluidics-enabled orientation and microstructure control of macroscopic graphene fibres


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.

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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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This work was supported financially by the US National Science Foundation under the award no. DMR 1742806. Thermal conductivity measurement of the macroscopic graphene structures was supported by the US National Science Foundation under the award CMMI 1463083.

Author information

G.X. and J.L. designed the research. G.X. and Y.D. designed the microfluidic channels. G.X and W.Z. collected and analysed thermal, mechanical and microstructure data. G.X., Y.D., J.C. and L.T.Z. performed computational fluid dynamics simulations. G.X., A.J.C., S.D. and J.L. co-wrote the paper. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Jie Lian.

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Further reading

Fig. 1: Size and shape confinements controlling sheet orientation in solution and thus the microstructure and mechanical properties of the annealed graphene structures.
Fig. 2: Contraction and step expansion flow patterns for horizontally and vertically aligned graphene structures.
Fig. 3: Shape and size confinements of microchannels on GO sheet alignment, shear stress/distribution and rheological properties of the fluidic flow.
Fig. 4: Influences of elongational and expansion flow patterns on GO sheet orientation degree and alignment.
Fig. 5: Super strong and highly thermally/electrically conductive graphene belts fabricated from flat microchannels.