4D printed bio-inspired mesh composite materials with high stretchability and reconfigurability

Strain engineering such as Kirigami design offers viable solutions for transforming rigid or even non-stretchable materials into highly stretchable structures, thus providing new opportunities for building flexible electronic devices with biological tissue-like mechanical properties. However, the stretchability of stretchable structures based on traditional Kirigami design strategies often relies on out-of-plane deformation, thus posing a great challenge for flexible electronic devices with high planarity requirements. Moreover, the low modulus properties of conventional soft materials also put forward new requirements for flexible electronic devices with complex mechanical environment adaptability. Here, Kirigami-like mesh composite materials (MCMs) based on shape memory polymer (SMP) and continuous carbon fibers, inspired by the laminar layout pattern of biological collagen tissues, were proposed and fabricated by 4D printing. 4D printed MCMs achieve elongation only through in-plane deformation and can combine excellent mechanical properties with high stretchability. The customizable fiber orientation enables MCMs with tunable stretchability from 1.8% to 375% and tensile modulus spanning four orders of magnitude from 0.04 MPa to 1375 MPa. In addition, owing to the variable stiffness properties and shape memory effect of SMP, it is also possible to achieve tunable stretchability and mechanical properties of MCMs with predetermined fiber orientation by controlling the ambient temperature, which facilitates the design of flexible electronic devices that conform to complex thermodynamic environments.