Fig. 3: Drawing-induced secondary structure rearrangement and mechanical reinforcement of DKBFs.
a A schematic depicts the reduction of fiber diameter and the transformation of β-sheet from α-helix during continuous mechanical drawing. b Representative SEM images of DKBFs under different drawing ratios exhibit a gradual decrease in fiber diameter (n = 3). c SAXS 2D patterns of DKBFs demonstrate an enhanced sharp orientation signal under varying drawing ratios from 1.0 to 3.0. d The azimuth (ϕ) plot of DKBFs under different drawing ratios reveals an increased orientation factor (f). e Changes in the secondary structure content of DKBFs with different drawing ratios are extracted from deconvolution analysis of the amide I/II region on the FTIR spectrum. f Representative stress–strain curves of DKBFs with different drawing ratios. g The breaking strength and toughness analysis of DKBFs with different drawing ratios. Data are presented as mean ± SD (λ = 1.0, n = 5; λ = 1.5, n = 9; λ = 2.0, n = 5; λ = 2.5, n = 7; λ = 3.0, n = 9). Statistical significance was determined by two-sample t-tests (OriginPro 2021). ns no significant difference; ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001. h A comparison of output breaking stress and toughness between our UKBFs, DKBFs, and other natural and artificial protein fibers. Note: DS denotes degummed silk46, RKF denotes regenerated keratin fiber24,27,30,34,51, RSF denotes regenerated silk fiber47,48, RSSF denotes recombinant spider silk fiber49,50, WF denotes wool fiber. Source data are available in the Source Data file.
