Bio-Inspired Gradient Heterogeneous Architectures for Ultrasensitive and Robust Strain Sensors via Programmable Crack Engineering.

The development of flexible strain sensors is crucial for next-generation wearable medical devices and human-machine interfaces (HMIs). While conductive networks based on random microcracks have been widely employed to enhance sensor responsiveness, they are often limited by trade-offs between sensitivity and measurement range. Inspired by the stress concentration mechanism in insect campaniform sensilla (CS), this study proposes a biomimetic heterogeneous bilayer strain sensor based on a deterministic macrostructure. The sensor employs a bilayer cladding architecture with a U-shaped cross-section and introduces a strain-dependent path switching (SDPS) strategy by modulating the conductivity gradient between the low-resistance core and the high-resistance cladding layer. Through this structure, the sensor achieves an ultra-high gauge factor (GF) of 301799, featuring an extremely low detection limit (0.067%) and excellent cycling stability (>11 000 cycles). By programmatically designing the crack geometry, the sensor demonstrates highly tunable sensitivity and range. Based on its exceptional performance, the sensor has been successfully applied to the monitoring of full-scale human physiological signals and integrated into a high-fidelity teleoperation system. This research not only provides a universal biomimetic paradigm for the design of high-performance flexible sensors but also lays the theoretical foundation for the industrial application of precision medicine and intelligent robotic skin.