Micropore Confinement in Flow Systems Enables Subsecond Bipolar ECL Biosensing

Bipolar electrochemiluminescence (BE-ECL) offers significant analytical potential, yet high operational voltages for nano/microscale bipolar electrodes and mobility constraints impede high-throughput applications. We engineer a dynamic BE-ECL platform using structurally optimized 10 mL centrifuge tubes as micropore-confined devices, where the gravity-driven translocation of functionalized SiO₂/CNT microbeads (SCBs) with a diameter of 160 μm through an embedded micropore generates spatiotemporally resolved subsecond ECL emission, captured by photomultiplier tube detection at a 12 V driving voltage (1.74 V/mm). Finite element simulations and experimental validation confirm synergistic field intensification from geometric confinement-polarization coupling, substantially reducing the operational voltages. Crucially, immobilized SCBs in the [Ru(bpy)₃]²⁺/TPrA system reveal distinct anodic ECL mechanisms: simultaneous direct oxidation at overpotential (10 V, 1.45 V/mm) versus coreactant-mediated excitation at threshold potential (5 V, 0.72 V/mm) via TPrA^•+ radical oxidation of [Ru(bpy)₃]²⁺. Functionalized SCB biosensors enable fg/mL-level quantification of human chorionic gonadotropin (HCG) through spatiotemporally resolved flow-through detection at 16 V (2.32 V/mm), establishing the practical viability of high-throughput suspension array biosensing.