A Zn-MOF-enhanced nanofibrous sponge-structured triboelectric sensor via humidity-induced phase separation for real-time impact monitoring in smart helmets

The integration of pressure-sensing materials into wearable protection systems has great potential for intelligent safety monitoring. While modern cycling helmets are effective at dissipating impact energy, they still lack real-time sensing and localization capabilities, hindering timely injury assessment. In this study, a humidity-induced phase separation electrospinning strategy (HIPS) is developed to produce an ultralight three-dimensional sponge-structured triboelectric sensor (3D-STS), in which polyacrylonitrile (PAN)/zinc-based metal-organic framework (Zn-MOF) composite is used as the core sensing material. Owing to its hierarchical 3D structure and well-dispersed Zn-MOFs, the 3D-STS exhibits improved mechanoelectric conversion performance, achieving a sensitivity up to 3.83 V/kPa in the low-pressure range 0.02–0.7 kPa. Furthermore, the as-prepared 3D-STS withstands impacts at up to 2 m/s while maintaining over 96% of its electrical output after 10,000 compression cycles, indicating its excellent mechanical durability. When sixteen 3D-STS units were integrated into a helmet to form a 16-channel sensing system, the system enabled real-time multisite impact monitoring through a LabVIEW interface and achieved over 95% accuracy in tests. This research overcomes the limitations of conventional helmet sensors in real-time pressure detection and opens new possibilities for smart, self-responsive protection systems.