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Materials Science in Additive Manufacturing Fibrous silk in biomedicine

and elastin, FS stands out with superior mechanical to conventional methods. This framework extends to
performance. 54 optimizing spinning flow rates, coagulation conditions,
In addition, the strength of FS surpasses that of and fiber drawing processes to enhance FS properties. 66,67
common degradable polymer biomaterials such as collagen In addition to process optimization, researchers have
and poly(L-lactic acid) (PLLA). Collagen bulk materials explored the integration of functional materials to tailor
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typically exhibit a strength range of 0.9 – 7.4 MPa and FS properties. Cheng et al. used molecular simulations to
polylactic acid between 15 MPa and 26 MPa. 55-57 In terms study graphene-peptide interactions, revealing significant
of toughness, FS also outperforms many synthetic fibers, enhancements in silk strength, elasticity, and overall
including Kevlar (50 MJ/m ), carbon fiber (25 MJ/m ), mechanical performance.
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wool (60 MJ/m ), and some collagen fibers like tendon In addition, studies have demonstrated that the
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collagen (7.5 MJ/m ). It is particularly noteworthy that mechanical performance of FS can be enhanced
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the exceptional stretchability and resilience of FS far by incorporating specific substances into artificial
exceed those of Kevlar fiber, which has long served as a feed, resulting in materials with superior strength
benchmark for high-performance fiber technology. 52,59 In characteristics. Zhang et al. reported that the
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addition, wild species-derived silks – so-called Tussah silks, incorporation of multi-walled carbon nanotubes, single-
including A. pernyi – have been extensively studied over the walled carbon nanotubes, lignosulfonate calcium, and
past decade. Guan et al. reported that A. pernyi cocoon graphene into mulberry leaves significantly improved
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exhibited superior mechanical properties, achieving a FS’s breaking stress, elongation, toughness, and tensile
tensile strength of 55 MPa and an elongation rate of 25%, strength. These findings were further supported by
compared to 25 MPa tensile strength and approximately independent studies. 71-73 Further additives – such as ionic
16% elongation for the domesticated B. mori cocoon. precursors, nano-hydroxyapatite, feather fibers, and metal
However, compared to natural FS, most regenerated nanodroplets – have also been employed to enhance FS
FS-based materials produced from SF solutions remain properties.
relatively fragile and prone to breakage. For instance, For instance, Guo et al. coated mulberry leaves
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regenerated FS membranes crafted from silkworm SF with CaCl , NaH PO , and nano-hydroxyapatite, which
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solutions exhibit a dry tensile strength of only 0.02 GPa with promoted an increase in α-helix and random coil content
a breaking elongation of <2%. These inferior mechanical within the FS secondary structure, thereby improving
properties are attributed to the disruption of the secondary mechanical properties. At low concentrations, the
and hierarchical structures compared to native FS. 61,62 To combination of Ca and PO yielded FS with a breaking
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improve the mechanical properties of regenerated FS, strength of 0.49 GPa, elongation of 13.01%, and toughness
researchers have investigated precise control over the of 0.023 GPa. At higher concentrations, these values
size, quantity, distribution, alignment, and nanoscale increased to 0.62 GPa strength, 17.42% elongation, and
spatial arrangement of crystalline and non-crystalline 0.022 GPa toughness. Both formulations exceeded the
domains. 11,44,63 Yazawa et al. introduced a cutting-edge tensile strength of natural silk (0.3 GPa), although with
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spinning methodology, employing tetrahydrofuran as slightly reduced elongation. Gao et al. encapsulated
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the coagulation solvent to inhibit the rapid formation of liquid metal nanodroplets in sodium alginate and
β-sheet structures. Subsequent post-stretching treatments sprayed the mixture onto mulberry leaves, resulting in
facilitated the controlled formation and alignment of FS with a tensile strength of 0.81 GPa and an elongation
β-sheets, substantially enhancing ductility and toughness, of 70%. Similarly, Lu et al. incorporated rare earth ions
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even surpassing that of natural FS. Such regenerated FS (La /Eu ) into the silkworm diet, which significantly
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may potentially serve as fibrous reinforcement materials. enhanced the mechanical properties of silk by increasing
To further expand FS’s mechanical capabilities, diverse β-sheet orientation and reducing fiber diameter. The
physical and chemical methods have been explored. Fang resulting silk exhibited a tensile strength of 0.97 GPa and
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et al. demonstrated that controlled-speed winding during toughness of 188 MJ·m , approaching the performance of
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FS production yielded fibers outperforming natural FS. Wet spider dragline silk.
spinning techniques produced artificial FS with 0.42 GPa Owing to their distinctive attributes – such as ease
strength, 47.1% fracture strain, and 154.8 MJ/m fracture of cultivation, short breeding cycles, and the ability to
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energy. Yao et al. applied rapid Bayesian optimization accumulate up to 25% pure protein – silkworms are
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technology to refine FS processing, achieving a 2.20-fold considered ideal candidates for recombinant product
increase in tensile strength, a 2.16-fold increase in modulus, delivery. Recent advances in genetic engineering have
and a 2.75-fold improvement in toughness compared enabled the transformation of silkworm FS into a platform
Volume 4 Issue 2 (2025) 5 doi: 10.36922/MSAM025130020