Closed-loop tactile-visual interactivity via chip-free luminescent fibers enabled by capacitive coupling

Smart textiles face inherent compromises between functionality and wearability due to rigid electronics and complex circuitry. Here, we introduce a touch-luminescence (TouchLumi) fiber that overcomes this trade-off by enabling chip-free, real-time tactile-visual interaction via electric field confinement. The fiber integrates a conductive core, a high-permittivity poly(vinylidene fluoride) hexafluoropropylene/barium titanate dielectric layer, and a copper ion-doped zinc sulfide electroluminescent sheath. Upon touch or conductor-induced capacitive coupling, dielectric mismatch concentrates the electric field within the emissive layer, driving localized and simultaneous high-brightness emission at a portable 3-volt power without requiring any other external field or support. This synergistic design merges tactile signal detection and visual feedback into a unified closed-loop system. Crucially, TouchLumi fibers are continuously producible with robust washability and textile compatibility, supporting digital embroidery and large-area machine weaving. We demonstrated its applications, including selective pattern illumination via wet-fingertip activation, multipoint responsive interfaces, and optical messaging through a keyboard textile. TouchLumi fiber enables intuitive tactile-visual interaction that unlocks transformative applications in assistive and inclusive communications.