Fig 1

Fabrication of graphene fibers and their fabrics by the template CVD method 36, 39, 40. (a) Schematic of the template fabrication process of the graphene fiber and graphene@PVA (G@PVA) fiber; (b-e) SEM images of the axial outer surface morphology of graphene fibers (b-c) and G@PVA fibers (d-e). scale bars, 40 μm (b and d) and 500 nm (c and e); (f) Photograph and SEM image of a G@PVA fiber wound on a plastic rod; (g-h) Electrical (g) and mechanical (h) properties of graphene with different amounts of PVA coating. The insets in (g) and (h) show the magnified I-V curves in the range of 4.2-5.5 V and the magnified strain-stress curve, respectively; (i) Schematic of the process for graphene woven fabrics (GWF) preparation; (j-k) Low-magnification (j) and high-magnification (k) SEM images of pristine GWF; (l) Optical images of flexible GWF/PDMS composite films. The inset shows the twisted GWF film by tweezers. (a-g) Adapted with permission from Ref. 36. Copyright 2015, American Chemical Society. (i, l) Adapted with permission from Ref. 39. Copyright 2019, Nature Publishing Group. (j-k) Adapted with permission from Ref. 40. Copyright 2019, Wiley-VCH."

Fig 2

Fabrication of the 3D graphene fibers by the secondary growth method 41. (a) Schematic of the preparation process of 3D graphene fibers (3DGFs); (b) SEM image of the 3DGFs; (c) Thickness of the graphene sheets in the inner parts of the 3DGFs grown for different time; (d-e) Electrical conductivity (σ) of the 3DGFs (d) and EMI SE of the 3DGF membranes (e) for different growth time and different thickness of graphene sheets. Adapted with permission from Ref. 41. Copyright 2018, Wiley-VCH."

Fig 3

Fabrication of porous graphene fibers by the film-scrolling method 44, 45. (a) Schematic of the film-to-fiber self-assembly process; (b-c) Low-magnification (b) and high-magnification (c) SEM images of the as-fabricated graphene fiber. The inset in (b) shows its current density-voltage curve, with a conductivity of 1000 S·m-1; (d) Representative Raman spectra of the graphene film and the further-fabricated graphene fiber; (e) Schematic models of the porous graphene fiber and the G/MnO2 composite fiber; (f) Comparison between the current-voltage (CV) curves of graphene fiber and G/MnO2 fiber at 10 and 200 mV·s-1; (g) Cycling stability of the graphene and G/MnO2 composite electrodes. The inset shows a comparison of typical charge/discharge cycles at a current density of 100 mA·cm-2; (h) Schematic of the fabrication process of GOF@G fibers; (i-j) Electrical (i) and mechanical (j) properties of rGOF and rGO@G fibers with the increasing number of graphene layers. (a-g) Adapted with permission from Ref. 44. Copyright 2011, American Chemical Society. (h-j) Adapted with permission from Ref. 45. Copyright 2019, the Royal Society of Chemistry."

Fig 4

Massive fabrication of GQF by a forced-flow CVD method 53. (a) Schematic of the experimental design; (b) As-grown GQF coiled on inner tube by APCVD (up), forced-flow CVD (middle) and LPCVD (down) method; (c) Raman spectra of graphene on quartz fiber obtained by APCVD (up), forced-flow CVD (middle) and LPCVD (down) respectively. Adapted with permission from Ref. 53. Copyright 2020, American Chemical Society."

Fig 5

The applications of GQF in the vapor sensors and electro-thermal devices 53. (a) Schematic (left) and optical image (right) of the bio-mimetic GQF sensors; (b) Resistance variation in response to acetone vapor under different carrier gas flow rates from 50 to 300 sccm (Standard Cubic Centimeter per Minute). The inset shows the zoom-in ?R/R0-t response curves; (c) The response signal over 5000 cycles under 150 sccm Ar flow; (d-e) A 40 cm × 200 cm further-weaved GQF fabric (GQFF, d) and the its sheet resistance mapping (collected from 11 × 11 points, e); (f) Time-dependent temperature variation of GQFF under different voltages; (g) Electro-thermal temperature of GQFF under different voltage; (h) Infrared image of GQFF heater under vacuum at an applied voltage of 24 V. Adapted with permission from Ref. 53. Copyright 2020, American Chemical Society."

Fig 6

Controlled growth of uniform graphene film on the hole surface of PCF 64. (a) Schematics of Gr-PCF grown by CVD method; (b) SEM image of Gr-PCF end surface; (c-d) 2D-mode Raman intensity mapping (c) and Raman spectrum (d) of graphene at fiber end surface; (e-f) Schematics of graphene growth in the micron-size holes of PCFs at APCVD (e) and LPCVD (f); (g) Representative Raman spectra of graphene at different positions of graphene ribbon film along the gas flow under APCVD (upper panel) and LPCVD (lower panel) growth conditions. (h) Statistics of ID/IG, I2D/IG and the FWHM of graphene Raman peak at different positions. Adapted with permission from Ref. 64. Copyright 2019, Nature Publishing Group."

Fig 7

Fabrication of N-doped graphene glass fibers by PECVD method and their HER performance 69. (a) Schematic of the copper foam-assisted PECVD process; (b) Raman spectra of N-doped graphene grown at 580 ℃ in comparison with pristine graphene grown under the same conditions; (c) SEM image of vertically oriented graphene wrapping directly grown on glass fiber; (d) Spatial distribution of the sheet resistance (2 cm × 2 cm) of the N-doped graphene grown on the glass fiber fabrics; (e, f) Polarization curves (e) and corresponding Tafel plots (f) of the pure glass fiber, non-doped graphene glass fiber, and N-doped graphene glass fiber. Adapted with permission from Ref. 69. Copyright 2019, the Royal Society of Chemistry."

Fig 8

CVD fabrication of graphene-metal fibers and their properties 70, 74, 75. (a) Schematics of the graphene-copper (G-Cu) fiber; (b) Raman spectrum of the graphene printing transferred to 300 nm Si/SiO2 substrate from Cu fiber; (c) SEM images showing different seed density of graphene on the Cu fiber (left) and on the Cu foil (right). Both samples were grown simultaneously; (d) Measurements of tensile stress and strain-to-failure of the G-Cu fiber and pure Cu fiber. All data were averaged from 15 fibers from each sample and deviations were below 5%. The inset shows the measurement set-up; (e) Temperature dependent resistivity of the G-Cu fiber and pure Cu fiber measured from room temperature to 175 ℃; (f) Calculated Cu volume after nitric acid, aqua regia, and 1 mol·L-1 ammonium persulfate treatments. Each etch rate was calculated by averaging the dissolution time obtained from 5 samples; (g) Schematic of the fabrication of the G-Cu nanofibers in PECVD system. The resulting G-Cu nanofibers were analyzed, followed by oxygen etching to obtain the same nanofibers without the graphene coating for a fair comparison; (h) SEM image of the as-grown G-Cu nanofibers; (i) Extracted values of thermal conductivity for G-Cu nanofibers of various dimensions. (a, c-f) Adapted with permission from Ref. 74. Copyright 2018, Elsevier Ltd. (b) Adapted from American Chemical Society publisher. (g-i) Adapted with permission from Ref. 75. Copyright 2015, American Chemical Society."