Fig. 5.

4D printing of SMPs. (a–f) 4D printing of PLA-based shape-changing leaves. (a) Schematic tri-layer configuration of a leaf showing two layers of PLA patterns (green) and one layer of ferromagnetic PLA (heater element). (b) Selective heating region of the leaves by microwave heating without heating the PLA stem. (c, d) Comparison of the shape-shifting process of the blooming leaves under (c) microwave selective heating of the leaves and (d) water heating of the whole structure. Reproduced with permission [112]. Copyright 2022, Elsevier B.V. (e–h) 4D printing of graphene/SOEA shape-morphing structures. (e) A series of structures mimicking flying actions of birds fabricated with SOEA with different graphene contents. (f) SLA-manufactured nerve guidance conduits without and with 0.8% GO. (g) A demonstration of the self-folding of a 4D structure to connect the broken nerve. (h) Immunofluorescence images of neurogenic differentiation of MSCs for UV cured conduit and 4D printed conduit. Reproduced with permission [77]. Copyright 2018, Wiley-VCH.