Hook-and-Loop-Inspired CNTs/CNFs Structure for Flexible Strain Sensors With Ultra-High Sensitivity and Wide Sensing Range.

The morphology and propagation behavior of channel cracks significantly influence the performance of crack-based thin film strain sensors. To date, flexible strain sensors still face a conflict between sensitivity and sensing range, which severely hinders their applications in flexible wearable electronics. Inspired by the hook-and-loop structure, this work proposed a multiscale design strategy and successfully constructed a composite film with a multi-path network structure via in situ growth of curved carbon nanotubes (CNTs) on carbon nanofibers (CNFs). Through the design of a micro-nano hierarchical structure, CNTs/CNFs sensor exhibits a segmental ultra-high sensitivity with a gauge factor of 5679.4 within the 120%-163% strain range, alongside a broad overall sensing range of up to 163%. The dense conductive network and bridging behavior of CNTs/CNFs film effectively resolves the problem of sensing failure in strain sensors under large strain, exhibiting excellent sensing performance over the entire monitoring range. Finally, we demonstrated the applications of CNTs/CNFs sensor with rapid response/recovery time and good sensing stability in encrypted information transmission, showing its great potential in the fields of health monitoring, human-machine interaction, and secure information transmission.