Fatigue‐Resistant Kirigami Ionic Skins for High‐Fidelity Strain Sensing and Rehabilitation Motion Recognition

ABSTRACT Stretchable ionic conductors are attractive for wearable electronics, yet combining high strain sensitivity, fatigue‐crack resistance, and cyclic electromechanical stability in an ionic‐skin platform remains challenging. Here, we develop fatigue‐resistant kirigami ionic skins based on elastic and tough segmented polyurethane ionogels. The ionic liquid preferentially plasticizes soft segments to form continuous ion‐transport pathways, while the hard segments act as reinforcing domains that redistribute stress and suppress crack initiation and growth. The optimized ionogel reaches 2533% stretchability, 125 MJ m −3 toughness, and 42.5 kJ m −2 fracture energy, with no measurable notch growth after 10,000 cycles at 100% strain. Leveraging this robust conductor, we pattern a single conductive track with a periodically repeated V‐shaped kirigami layout and laminate it onto an elastomeric backing to enable geometric strain amplification with reversible cut opening and closure. The ionic skins reach a gauge factor of ∼65, show low hysteresis (<5%), and sustain stable response over 1000 cycles, while exhibiting weak cross‐talk to superimposed normal pressure and a response time of ∼120–140 ms. Feature extraction plus an artificial neural network (ANN) classifier enables ≈99% recognition of graded knee motions. This materials‐architecture‐data strategy offers a scalable route to fatigue‐resistant, high‐fidelity ionic skins for soft electronics and rehabilitation interfaces.