Structural–Thermodynamic Codesign of Spine-Guided Cracks for Full-Spectrum Strain Sensing with Intrinsic Thermal Compensation

Abstract Flexible strain sensors face a long-standing trade-off between ultralow limit of detection (LOD) and wide linear working range, limiting full-spectrum strain monitoring within a single device. This challenge is further amplified in thermomechanically coupled environments, where temperature fluctuations distort strain readout and compromise measurement fidelity. Here, we report a structural–thermodynamic codesign strategy implemented in a flexible strain sensor with spine-guided cracks for full-spectrum sensing with intrinsic thermal compensation. The sensing layer integrates a carbon nanotube (CNT) conductive network with controlled microcracks and biomimetic spine-like protrusions. Pre-engineered microcracks amplify resistance modulation at small strains, enabling an ultralow LOD of 0.02% strain. At large strains, spine-like protrusions deflect propagating cracks, redistribute local stress, and suppress catastrophic crack coalescence, extending the linear sensing range to 250% with 97.5% linearity. Meanwhile, the negative temperature coefficient of resistance (TCR) of the CNT network is counterbalanced by crack widening induced by thermal expansion of the addition-cure silicone elastomer substrate, yielding a low full-window TCR of 9.98 × 10−6 °C−1 over 30–70 °C without external calibration or auxiliary circuitry. The sensor further shows stable operation under varying humidity and enables physiological motion monitoring, deformation tracking of solid rocket propellant, and in situ detection of lithium-ion battery swelling. These results highlight a practical route toward full-spectrum, reliable flexible strain sensors for thermomechanically coupled conditions.