FIG. 3.

Additive manufacturing techniques to produce fibers. (a) A visual representation of printing fibers using a rotating nozzle to create a helical pattern. Reproduced with permission from Ref. 73. (b) Structure of fibers manufactured through direct printing, made of CNT core and silk fibroin sheath. Reproduced with permission from Zhang et al., Matter 1, 168 (2019). Copyright 2019 Elsevier.⁷⁴ (c) Cartilage Scaffolds realized by extrusion printing. Reproduced with permission from Sun et al., Sci. Adv. 6, eaay1422 (2020). Copyright 2020 Authors, licensed under a Creative Commons Attribution (CC BY) license.⁷⁵ (d) Schematics of direct writing EHD printing setup. Reproduced with permission from Kong et al., Nat. Commun. 11, 1435 (2020). Copyright 2020 Authors, licensed under a Creative Commons Attribution (CC BY) license.⁷⁶ (e) Crossing of three fibrous walls printed by EHD printing, made from polyethylene oxide ink mixed with Ag nanoparticles. Reproduced with permission from Liashenko et al., Nat. Commun. 11, 753 (2020). Copyright 2020 Authors, licensed under a Creative Commons Attribution (CC BY) license.⁷⁷ (f) Layer by layer assembly of microfiber realized by EHD printing. These 10 μm size fibers are made from Poly Lactic-co-Glycolic Acid (PLGA). Reproduced with permission from Moon et al., Sci. Adv. 7, eabf5289 (2021). Copyright 2021 American Association for the Advancement of Science.⁷⁸ (g) Inflight printing of silver and PEDOT:PSS fibers. (h) Suspended, aligned arrays of Silver/PEDOT:PSS fibers realized by inflight printing. (i) SEM image of curved nanofiber mesh produced by inflight printing. (g)–(i) Reproduced with permission from Wang et al., Sci. Adv. 6, eaba0931 (2020). Copyright 2020 Authors, licensed under a Creative Commons Attribution (CC BY) license.⁸² (j) Schematic illustration of flow-focusing, microfluidic setup. (k) Dried spun fibers made from protein nanofibrils mixed with polysaccharide and alginate coflowing with polyethylene glycol are realized by microfluidic fiber printing. (l) SEM image of the microfluidic-printed fiber with tightly packed bundles on its surface. (j)–(l) Reproduced with permission from Kamada et al., Small 16, e1904190 (2020). Copyright 2020 John Wiley and Sons.⁸⁴