Fig 1

Typical carbonaceous fibers: carbon fibers, carbon nanotube (CNT) fibers 8, and graphene fibers (GFs) 9, 11. Adapted with permission from Ref. 8. Copyright 2010, American Chemical Society. Adapted with permission from Ref. 9. Copyright 2011, Nature Publishing Group. Adapted with permission from Ref. 11. Copyright 2016, Wiley-VCH."

Table 1

Comparison of different carbonaceous fibers."

Fig 2

Various spinning methods for GFs. (a) The knot of GF 9. Adapted with permission from Ref. 9. Copyright 2011, Nature Publishing Group. (b) Schematic illustration of wet spinning of GOFs, followed by chemical or thermal reduction to transform GOFs into GFs. (c) 50-filament GOFs extruded from the spinneret. (d) Images of ultrafine GFs 11. Adapted with permission from Ref. 11. Copyright 2016, Wiley-VCH. (e) Illustration of the dry spinning process to form a GOF 29. Adapted with permission from Ref. 29. Copyright 2017, the Royal Society of Chemistry. (f) Dry-jet wet spinning of GFs. (g) Surface morphology of GF. (h) Cross-section morphology and the schematic of GF 30. Adapted with permission from Ref. 30. Copyright 2013, American Chemical Society."

Fig 3

Fabrication of GFs through space-confined hydrothermal strategy, and film conversion, and CVD method. (a) Photograph of GF coiled around a glass rod. (b) Surface morphology of GF 31. Adapted with permission from Ref. 31. Copyright 2012, Wiley-VCH. (c) GFs with multichannels 33. Adapted with permission from Ref. 33. Copyright 2012, American Chemical Society. (d) A thin GO film being scrolled into a GOF. (e) Different morphologies of GOFs 35. Adapted with permission from Ref. 35. Copyright 2014, American Chemical Society. (f) Quartz fiber bundles before (white) and after (grey) graphene growth. (g) Morphology of GF after etching the quartz fiber 40. Adapted with permission from Ref. 40. Copyright 2020, American Chemical Society."

Table 2

Summary of the preparation methods and properties of GFs."

Fig 4

Various strategies to enhance the mechanical properties of GFs. (a) Schematic of the basic structure of GOFs and GFs based on the large-sized and small-sized GO. (b) Tensile strength of different GFs 61. Adapted with permission from Ref. 61. Copyright 2015, AAAS. (c) Typical stress-strain curves of GFs derived from different coagulation baths 60. Adapted with permission from Ref. 60. Copyright 2012, Wiley-VCH. (d) Schematic of high-strength GFs fabricated by a full-scale synergetic defect engineering to minimize the defects. (e) Tensile strength curves of GFs treated with different temperatures 11. Adapted with permission from Ref. 11. Copyright 2016, Wiley-VCH. (f) Schematic of phenolic carbon strengthening GFs. (g) Stress-strain curves of different GFs 65. Adapted with permission from Ref. 65. Copyright 2016, American Chemical Society. (h) Illustration of the fabrication of the GFs via sequential toughening of hydrogen (chitosan) and ionic bonding (Ca2+) 66. Adapted with permission from Ref. 66. Copyright 2018, American Chemical Society."

Fig 5

Various approaches to enhance the electrical and thermal properties of GFs. (a) Electrical conductivity of GFs annealed at different temperatures from 1573 to 3273 K 11. Adapted with permission from Ref. 11. Copyright 2016, Wiley-VCH. (b) Structural model of GF. (c) Schematic of GFs doped by dopants, the dopant molecules marked by red dots were FeCl3, Br2, or K. (d) Comparison of electrical conductivity of GFs and doped ones 77. Adapted with permission from Ref. 77. Copyright 2016, Wiley-VCH. (e) Thermal conductivity of GFs. (f) Heat transport of different GFs and copper wire 61. Adapted with permission from Ref. 61. Copyright 2015, AAAS."

Fig 6

GFs for multifunctional fabrics, sensors and actuators. (a) Br2 doped GFs connecting the working lamp (220 V, 9 W) 77. Adapted with permission from Ref. 77. Copyright 2016, Wiley-VCH. (b) A thermally annealed GF fabric with porous feature. (c) Infrared picture of GF fabric heater 86. Adapted with permission from Ref. 86. Copyright 2016, Nature Publishing Group. (d) PVA/GF as a strain sensor 57. Adapted with permission from Ref. 57. Copyright 2015, American Chemical Society. (e) GFs and Pt-GFs-based humidity sensor 87. Adapted with permission from Ref. 87. Copyright 2018, Wiley-VCH. (f) Scheme for the responses of two twist GOFs suffering the wetting of acetone. (g) GOFs woven with cotton fibers for an actuator 88. Adapted with permission from Ref. 88. Copyright 2019, the Royal Society of Chemistry."

Fig 7

GFs for fiber-shaped supercapacitors and batteries. (a) Morphology of a GF covered with 3D porous network-like graphene framework (GF@3D-G). (b) Two twined GF@3D-Gs with polyelectrolyte for fiber-shaped supercapacitor32. Adapted with permission from Ref. 32. Copyright 2013, Wiley-VCH. (c) Coaxial wet-spinning process to prepare core-sheath fibers. (d) Coaxial fibers woven with cotton fibers. (e) Performance comparison of this supercapacitor with the previous fiber-shaped ones 27. Adapted with permission from Ref. 27. Copyright 2014, Nature Publishing Group. (f) Graphene@polymer core-shell fibers for high-performance wearable supercapacitors, which could light a green LED. (g) Capacitance retention of wearable supercapacitors under the bending angle of 180° 96. Adapted with permission from Ref. 96. Copyright 2017, American Chemical Society. (h) Schematic illustration of the graphene/CNT composite fiber. (i) Current density-voltage curves of wire-shaped dye-sensitized solar cells with different fibers as the counter electrodes. (j) The flexible photovoltaic textile 99. Adapted with permission from Ref. 99. Copyright 2014, Wiley-VCH."