Autonomously self-healing and ultrafast highly-stretching recoverable polymer through trans-octahedral metal-ligand coordination for skin-inspired tactile sensing

•Highly stretchable and self-healing materials based on metal–ligand coordination.•Choice of solvents can significantly affect the results of fabricated products.•SAXS/WAXS models constructed under different scenarios.•Robust skin-inspired pyramidal sensors can be performed over 100 cycles. Self-healing and stretchable materials have attracted considerable attention due their wide potential applications in developing human–machine interfaces. However, it remains a great challenge to achieve polymeric materials capable of both self-healing at room temperature and fast elastic recoverability after cuts or high stretching. We report herein a new material based on tolylene 2,4-diisocyanate elastomer (PTD) terminated with 4,4′-Bis(hydroxymethyl)-2,2′-bipyridine (bpy), having autonomously self-healing and ultra-fast stretching recovery properties, through incorporating trans-octahedral metal–ligand coordination of Zn2+ or Ni2+ ions with the bpy moieties; both Zn- and Ni-bpyPTD show combined properties of water-resistant, anti-bacteria, low toxicity and high transparency, and of respective emphases in self-healing and mechanical strength. The underlying mechanism is associated with the trans-octahedral metal–ligand coordination and their organized nanostructures as effective crosslinking sites in the bpyPTD matrix of rich hydrogen bonding, as revealed by X-ray absorption and in-situ small- and wide-angle X-ray scattering. Particularly, when fabricated into a pressure sensor, Ni-bpyPTD exhibits synchronized and durable mechanical and electrical responses under a repetitive cycling tensile testing up to 300% strain within 60 s, over 100 cycles, and would serve as a promising material for skin-inspired tactile sensing.