Stretchable h‐BN/TPU Fibers for Passive‐Active Dual‐Mode Thermal Management and Wearable Haptic Interfaces

ABSTRACT Wearable thermal interfaces require rapid, spatially confined thermal feedback together with mechanical compliance, yet existing passive thermal‐management textiles and active thermal‐haptic devices remain largely separate. Here, a stretchable h ‐BN/TPU composite fiber is developed by coupling microfluidic spinning with non‐solvent‐induced phase separation. Rectangular‐channel confinement aligns hexagonal boron nitride plates within a microporous thermoplastic polyurethane matrix, constructing directional heat‐conduction pathways while preserving large deformation. The optimized 30 wt.% h ‐BN/TPU fiber achieves a dry‐state thermal conductivity of 2.08 and 4.14 W·m −1 ·K −1 under humid conditions, together with 9.67 MPa tensile strength and 422% elongation at break. Pareto‐front analysis identifies the 30 wt.% composition as the thermal‐mechanical knee, arising from the coupled effects of filler orientation, low void fraction, and deformable TPU domains. Woven h ‐BN/TPU fabrics provide passive thermal management, reducing surface temperature by 5.7°C under simulated solar irradiation and maintaining performance after 2000 bending cycles. When integrated into a thermal feedback glove, the fabric enables localized fingertip actuation with a heating rate of +29.55°C·s −1 and a thermal relaxation time of ∼20 s (returning below the warm perception threshold of 35°C). This fiber platform bridges passive heat regulation and active thermal haptics for next‐generation thermally interactive wearables.