Fig. 2: Characterization of the macroscopic mechanical properties and microscopic structures of E-GES.

a Stress-strain curves of different E-GES samples. b Stress-strain curves of 5% E-GES at different strain rates. The E-GES sample can resist the increasing strain rate without showing brittle fracture and exhibits a rising tensile toughness, meaning the breakage of more dynamic chemical bonds in the tough E-GES network to dissipate energy when a high tensile rate is applied. c Maximum tensile strain comparison between protein-based e-skins and synthetic material-based e-skins. d, e Calculated secondary structure results of the control sample (d) and 5% E-GES (e) from the analysis of the amide I band in their FTIR spectra (Supplementary Fig. 1). The peaks within the range of 1610-1640 cm⁻¹ are attributed to β-sheets, filled with blue (d) and brown (e) colour, respectively. Inset: Content of β-sheets and EGaIn in the E-GES network. f DSC thermograms of different E-GES samples. g Frequency sweep curves of G′ and G′′ for the control sample and 5% E-GES. h Schematic illustration of the stretching process of E-GES. The presence of EGaIn-SH coordinative bonds and the intermolecular H-bonds of β-sheets favour energy dissipation. i Photographs of the inflation process of E-GES. The E-GES sample can be sealed on the inflation port (port diameter of 1 cm) of an air pump and then inflated into a large balloon.