Terahertz liquid networks: a mesoscopic passive architecture for circumventing physical deadlocks in brain-computer interfaces.

Brain-computer interfaces (BCIs) for major neurological disorders face physical and physiological limitations. Mechanical mismatch in rigid microelectrode arrays precipitates chronic immune rejection and irreversible central nervous system damage, whereas bandwidth scaling in traditional wireless links inevitably breaches the 1 °C tissue thermal safety threshold. To circumvent this deadlock among bandwidth, heat dissipation, and biocompatibility, this review proposes the "terahertz liquid network" architecture. Utilizing injectable plasmonic nanoparticles as free-floating relay nodes, this architecture fundamentally abolishes the mechanical shear stresses characteristic of conventional implant interfaces. Exploiting broadband and dielectric properties of terahertz (THz) waves, the network achieves cross-scale bioelectronic integration across both physical and physiological boundaries. For communication and decoding, the system bypasses the strong THz absorption barrier of brain tissue via non-line-of-sight multipath scattering and THz-photoacoustic cross-modal transduction. Integrating these mechanisms with passive backscattering fulfills the terabits-per-second (Tbps) absolute bandwidth requirements dictated by full-cortical, high-fidelity motor decoding. For neuromodulation, specific THz photon energies are directed at voltage-gated ion channels to induce targeted non-thermal resonance, mediating precise, subcellular-level interventions devoid of macroscopic current overflow. Through an analysis of typical clinical scenarios-namely, audiovisual perception reconstruction and physical neural injury rehabilitation-this review demonstrates the feasibility of this architecture in resolving the conflict between high-throughput concurrency and stringent physiological constraints. Ultimately, the terahertz liquid network reconfigures the neural interface paradigm from a macroscopic active solid-state to a mesoscopic passive liquid-state. This transition grants the system superior biocompatibility and endows it with disease-modifying potential targeting underlying pathologies, establishing a trajectory for next-generation BCIs.