Hybrid BaTiO₃-MXene-graphene metasurface biosensor for ultra-sensitive terahertz detection of waterborne bacterial pathogens

The detection of waterborne bacterial pathogens at trace concentrations remains a major obstacle in environmental and public health monitoring. This study introduces a terahertz hybrid metasurface biosensor combining barium titanate (BaTiO₃), MXene, and graphene to enable high sensitivity and real-time detection. Electromagnetic simulations in COMSOL Multiphysics show a peak sensitivity of 244 GHz/RIU, a figure of merit of 3.484, and quality factors between 6.829 and 6.986. The resonance frequency shifts exhibit a strong linear relationship (R 2 > 0.99) with bacterial concentration, while transmittance ranges from 43.346 % to 43.982 % across refractive indices of 1.33–1.3921 RIU. Modulating the graphene chemical potential between 0.1 eV and 0.9 eV enhances tunability, and the sensor maintains stable performance at incident angles from 0° to 80°. Machine learning analysis confirms predictive precision with mean squared errors of 6 × 10 −6 –9 × 10 −6 and R 2 values above 0.9997. The proposed metasurface biosensor provides a scalable, label-free, and highly responsive platform for detecting waterborne pathogens in environmental, clinical, and water quality applications.