Nonequilibrium Interfacial Complexation Fibers With Programmable Ionic Memory

ABSTRACT Emulating learning and memory functions of biological systems in soft, textile‐compatible materials remains challenging, particularly for artificial synapses that require both structural adaptability and reliable ionic dynamics. Existing artificial synaptic devices predominantly rely on membrane‐based or multilayered architectures, which complicate fabrication and limit scalability. Here, we report multiscale interfacial polyelectrolyte complexation (IPC) fibers fabricated via a one‐step interfacial process, enabling programmable fiber architectures with mechanical compliance and direct compatibility with smart textile platforms. The IPC fibers exhibit hierarchical structures spanning nanometer to micrometer length scales, promoting confined ionic transport and slow relaxation dynamics within flexible, thread‐like conductors. As a result, fiber‐based artificial synapses display pronounced short‐term plasticity with a tunable slow relaxation time constant ( τ 2 ), which spans several orders of magnitude and reaches up to 40 min owing to multiscale ion trapping and migration. Moreover, woven fiber arrays demonstrate both temporal and spatial summation of synaptic responses, enabling time‐dependent learning and pixel‐level memory encoding in IPC fiber arrays. The facile, environmentally benign fabrication strategy, combined with intrinsic structure‐function coupling in IPC fibers, establishes a versatile material and device platform for potential smart textiles, wearable neuromorphic systems, and adaptive fabrics.