Syringe needle spinning of recombinant silk fibres with the H(AB)12 polymer dissolved in HFIP: (a) bright-field microscopic images of spun fibres in bundle in the coagulation bath and (b) SEM images of the separated fibre after rehydration, showing a relatively uniform fibre diameter of ∼8 μm. In addition, H(AB)12 polymer dissolved in LiBr aqueous solution can also form thinner silk fibres without bundling: (c) bright-field microscopic images in the coagulation bath and (d) SEM images of the dried fibre showing a diameter of ∼3 μm. Mechanical properties of syringe needle spun silk fibres using the H(AB)12 sequence dissolved in two different solvents (HFIP and LiBr aqueous solution). The effect of hydration on fibre Young's modulus is studied by comparing air dried and rehydrated fibres. (e) The Young's modulus maps (top) and the corresponding Young's modulus distributions (bottom) of the four different types of fibres were obtained using the similar nanoindentation measurement as in Supplementary Fig. 5b. The red colour in the Young's modulus map indicates outliers with extremely high Young's modulus values. (f) Averaged fibre Young's modulus values over the distribution plots in e, showing standard deviations. (g) Representative stress-strain curve from mechanical tensile testing on various silk fibre samples, confirming high fibre robustness and Young's modulus.