Mechanically robust, shape memory, self-healing and 3D printable thermoreversible cross-linked polymer composites toward conductive and biomimetic skin devices applications

The current work demonstrates excellent thermal, mechanical, shape memory, and self-healing properties of 3D printable, thermoreversible, cross-linked network composites. The thermoreversible cross-linked networks are composed of Diels-Alder (DA) reversible covalent and transient cross-links, which are formed by thermoplastic polyurethane (TPU) and poly(ε-caprolactone) (PCL). Also, cellulose nanocrystalline (CNC) is utilized as a cross-linking agent. The incorporated CNC, modified with furan (CNC-FA) and maleic anhydride groups (CNC-MAH), exhibits excellent compatibility with TPU/PCL matrix, forming physical and chemical cross-linking structures in the composites. Also, the mechanical properties , thermal stability, and self-healing properties are significantly improved after the addition of modified CNC. In addition, the mechanism of performance enhancement is further analyzed by molecular dynamics simulations. One should note that the mechanically robust and 3D printable self-healing composites enable the fabrication of durable conductive devices and biomimetic skin devices with high mechanical integrity, excellent electrical healing and superior strain-induced fluorescence properties, showing promise in next-generation flexible electronics, encryption devices and electronic skins, and may broaden the variety and applications of 3D-printable materials.