A Self-Powered Sensing Platform Based on the Janus Heterostructure for Machine Learning-Assisted Dual-Mode Detection of 17β-Estradiol

Interfacial energy level mismatch and inefficient charge extraction at bioelectrochemical interfaces have remained major bottlenecks for enzymatic biofuel cell-based self-powered sensing systems. Here, we reported a built-in electric field (BIEF) enabled self-powered sensing platform for intelligent dual-mode detection of 17β-estradiol (E2), featuring an energy level engineered Janus bioanode that uses work function differences to drive directional charge extraction during cascade biocatalysis. The Janus heterointerface was constructed by Zn–O–Ti coordination between unsaturated Zn 2+ sites in ZIF-8-NH 2 and -O-terminated Ti 3 C 2 T x, inducing an intrinsic BIEF and strengthened interfacial electronic coupling. Density functional theory calculations revealed favorable energy level alignment between the enzymatic redox donor FADH 2 (−4.73 eV) and the Zn–O–Ti interface (−5.11 eV), enabling low barrier electron injection and enhanced bioelectrocatalysis. For E2 sensing, an aptamer triggered hybridization chain reaction regulated methylene blue loading on the biocathode, converting target recognition into coupled electrochemical and optical outputs. The enzymatic biofuel cell was integrated on a screen-printed electrode with an IoT connected voltmeter for real-time wireless readout, while machine learning-assisted fusion improved analytical robustness in piped water, lake water, and human serum. This work highlighted Janus interfacial energy level engineering as a general strategy for regulating charge transfer in bioelectrochemical systems.