A non-percolating interfacial microcapacitor architecture decouples polarization enhancement from leakage suppression in humidity-tolerant polymer films

Sustainable polyesters are attractive triboelectric materials for low-frequency energy harvesting, but their practical use is limited by humidity-induced charge dissipation and insufficient mechanical durability. Here, we report a non-percolating interfacial microcapacitor architecture (IMCA) that decouples polarization enhancement from leakage suppression in immiscible polymer blends. Using a Pickering-emulsion-assisted melt-processing strategy, trace amounts of carbon nanotubes (CNTs) are selectively localized at the interface of polylactic acid/polybutylene succinate (PLA/PBS) blends, forming conductive shells around elongated dispersed domains. At 1 wt% CNT loading, these isolated interfacial shells create an optimal non-percolating regime: they enhance Maxwell-Wagner interfacial polarization and deep charge trapping, generate localized internal electric fields that help confine charges, and prevent the formation of continuous leakage pathways. As a result, the optimized triboelectric film delivers an open-circuit voltage of 185.7 V and a peak areal power density of 968.5 mW m^-2, retains 93.8% of its output voltage at 90% relative humidity, and remains stable over more than 12 000 cycles. The IMCA strategy is applicable to multiple immiscible polymer blends and is compatible with melt extrusion and film blowing. These findings establish a scalable interfacial design strategy for humidity-tolerant, mechanically robust triboelectric polymer films and related electroactive polymer systems.