Nickel Fiber Array‐Based Bilayer Heterostructures for Ultrahigh Sensitivity and Wide‐Range Strain Sensing in Multiscale Applications

Abstract The incompatibility between high sensitivity and wide detection range remains a critical scientific challenge in the field of flexible and wearable strain sensors. To address this, this study proposes an innovative strategy based on a bidirectional size‐separation and strain‐sharing synergy using nickel fiber arrays (NFAs). By constructing an aligned NFAs network through magnetic field assembly and combining with drop‐coating encapsulation, a bilayer NFAs/PDMS anisotropic composite sensor is fabricated. Its dimensional decoupling characteristic decouples strain transfer at the microscale (fiber surfaces) and nanoscale (fiber ends), transforming the traditional positive resistance‐strain response in the thickness direction into a negative resistance‐strain effect, which significantly enhances small deformation detection capability (GF = 558 under 0–15% strain, minimum resolution = 0.0033%). The bilayer's soft‐rigid synergistic strain sharing alleviates stress concentration in anisotropic deformation (GF = 20548 under 25–65% strain) and extending the max range to 80%. Different from traditional positive resistance‐strain sensors, this tunneling effect‐driven negative resistance‐strain effect fundamentally resolves the contradiction between high sensitivity and large measurement range. It enables simultaneous detection of facial micro‐expressions, whole‐body joint movements, and has been successfully applied to a quadruped robot posture detection system, realizing collaborative perception of complex postures and movements.