Core-Sheath Graphene Yarn Sensors for Versatile Wearable Pressure Monitoring

To address the demand for high-performance flexible pressure sensors in wearable electronics, this study proposes a fabrication method for graphene-wrapped yarn piezoresistive sensors with a core-sheath structure. Using a stainless-steel sewing thread as the conductive core and graphene-coated conductive nylon monofilament as the functional wrapping layer, the yarn twist parameters (1500–3500 T/m) were optimized through controlled wrapping process to systematically investigate the structure-performance quantitative relationship. Results demonstrate that the 3000-T/m sample exhibits optimal sensitivity in the medium-to-high pressure range (1–25 N; ${S} =0.037$ /N at 25 N), whereas the 2500-T/m sample achieves significantly enhanced sensitivity in low-pressure regime (<1.0> ${S} =9.37$ /N at 0.05 N), representing a nearly threefold improvement over its 1500 T/m counterpart (<1.0> ${S} =3.12$ /N at 0.05 N). Moreover, the sensor demonstrates broad detection range (0.01–25 N), fast response time (0.4 s), and excellent cycling stability (no degradation after 7000 compression cycles). Through embroidery and weaving techniques, we fabricated finger-joint motion-monitoring gloves, plantar pressure-sensing insoles, and a $16\times 16$ sitting posture pressure matrix, validating its multiscale application potential in human motion capture and body pressure monitoring. This work provides a novel strategy for developing highly sensitive and customizable textile-based electronic sensors, advancing the practical implementation of wearable health monitoring technologies.