Figure 1: Ink development and fabrication process.

(a) The chemical structures for epoxidized soybean oil (ESBO) and bisphenol F diglycidyl ether (BFDGE) starting materials used to prepare the base resin are shown. (b) Scanning electron micrograph of carbon nanofiber fillers, which are dispersed in acetone with sonication. The CNF suspension is added to the base resin with centrifugal mixing and acetone is removed resulting in the non-Newtonian inks shown in the optical image in (c). The ink then 3D printed through a micro nozzle to print complex 3D architectures as depicted in the schematic illustration in (d). At this point, two routes for final parts are available. Route 1 is shown in (e) where the printed part is thermally cured at 80 °C for 16 h, and then post cured at 150 °C for 2 h to obtain the printed primary shape. Alternatively, route 2 is shown in (f) where origami is used to fold the part after an initial partial cure at 80 °C for 4 h followed by (g) full curing of the folded part at 80 °C for 12 h with a post-cure at 150 °C for 2 h. The two routes converge at the programming step in (h) where part is heated to 80–100 °C for 5 min and programming is performed by applying an external stress to deform the part and maintaining the shape until the temperature is decreased to 20 °C for 2 min. Finally, the deformed part can recover to the original shape by thermal or resistive heating shown in (i). A range of 3D parts with complex geometries are shown in (j). The scale bar for (b) is 1 μm and for (j) is 1 cm.