Flexible Implantable Brain‐Computer Interface Electrodes: Advances in Materials and Structural Design

Implantable brain‐computer interfaces are undergoing a paradigm shift from rigid silicon architectures to soft, structurally adaptive systems capable of seamless, long‐term integration with neural tissue. Driven by breakthroughs in materials science and micro/nanofabrication, these next‐generation systems achieve unprecedented mechanical compliance, robust interfacial adhesion, and high‐fidelity neural recording. This review comprehensively summarizes the material and structural innovations propelling this evolution. We systematically categorize recent developments by electrode dimensionality: 1D fibers for minimally invasive deep‐brain targeting, 2D flexible arrays for expansive cortical mapping, and 3D microarchitectures for volumetric recording and stimulation. Crucially, we examine the synergy between structural engineering and advanced functional materials such as conductive polymers, carbon nanomaterials, and bio‐derived hydrogels to optimize neural interface and suppressing neuroinflammatory cascades. We further explore how emerging dynamic systems including stimuli‐responsive, self‐healing, and bioresorbable materials impart adaptive functionalities to sustain chronic operation. We also discuss multimodal integration of electrical, optical, and acoustic modalities, as well as ongoing efforts toward miniaturization, standardization, and clinical translation. Finally, we outline future directions toward intelligent, bioresorbable, and AI‐integrated neural interfaces that promise to achieve seamless, bidirectional communication with the human brain.