Extended Data Fig. 9: Rheology, mechanical testing and MM3D printing of flexible and stiff epoxy inks.

a, Storage (G′) and loss (G″) moduli versus shear stress for flexible (grey) and stiff (orange) epoxy inks. b, Apparent viscosity of flexible (grey) and stiff (orange) epoxy inks as a function of shear rate. c, Complex viscosity of flexible (grey) and stiff (orange) epoxy inks measured over time using a rheometer at room temperature. d, Storage and loss moduli of flexible (grey) and stiff (orange) epoxy inks as a function of frequency. e, Photograph of a printed epoxy (flexible) hinge that connects two printed epoxy (stiff) regions. Scale bar, 2 mm. f, Cyclic tests carried out at a frequency of 0.5 Hz with bending angles ranging from 18° to 142°. The results reveal that the material can sustain 1,632 ± 217 (mean ± s.d., n = 6) cycles before failing. (We note that failure is observed to occur within the flexible epoxy hinge, not at the stiff–soft interfaces.) g, Image sequence generated from multiple photographs of a Miura fold at various steps of folding (expanded side length, 64 mm).