Zr4 + /Al3+ coordination flame-retardant waterborne polyurethane/collagen fiber flexible sensing material for posture monitoring and robotic sensory skin in extreme environments

Natural polymers have emerged as pivotal materials for flexible sensors due to their inherent biocompatibility, biodegradability, and complex supramolecular structures and abundant functional groups of these polymers provide a substantial number of binding sites for the composite of conductive structural units. Despite these advantages, conventional natural polymer-based sensors exhibit limited operational stability under extreme environmental conditions. To address this challenge, we develop a flexible sensing material (PCM) through Zr 4+ /Al 3+ coordination crosslinking, integrating collagen fiber's hierarchical network with phosphorous-containing WPU (P-WPU) and carboxylated multi-walled carbon nanotubes. The optimized PCM demonstrates good pressure sensitivity (0.69 kPa −1 ) across a broad detection range (1.81–130.66 kPa), rapid response/recovery (100 ms each), and remarkable cyclic stability (>12,000 cycles). Moreover, the PCM exhibits outstanding flame retardancy with a limiting oxygen index (LOI) of up to 25.17 %.Furthermore, tests in simulated extreme environments demonstrated the stability of PCM in extreme conditions (-40–85 ℃, pH 1–13). PCM enables motion capture in extreme environments and can even serve as an intelligent skin for robots. This study proposes a novel, eco-friendly approach to the development of flexible sensors and offers a novel concept for sensing applications in extreme environments.