Multiresonant Membrane Metasurfaces for Multifunctional Molecular Absorption Sensing and Real Time Biochemical Tracking

Label‐free identification and real time tracking of biochemical substances became critical for molecular diagnostics and chemical analysis, yet conventional resonant terahertz (THz) metasurface sensing relies on a single resonance, limiting spectral selectivity and dynamic capability. Here, we suggest multiresonant membrane metasurfaces and employ them for simultaneous static characteristic absorption detection and dynamic reaction monitoring within a single pixel. We consider a membrane metasurface supporting multiple quasi‐bound states in the continuum designed at target frequencies and enabling the tailoring of the field enhancement and frequency‐selective interaction with target analytes. As a proof‐of‐concept, we achieve label‐free detection of the characteristic absorption features of pefloxacin at 0.78 and 0.99 THz, and real time tracking of vitamin C oxidation and denaturation under ambient conditions. The kinetic profiles extracted from the THz amplitude evolution show excellent agreement with nonlinear reaction models (R 2 > 0.92), demonstrating quantitative biochemical tracking capabilities. Our results establish a versatile and scalable THz photonic platform that unifies static molecule identification and dynamic reaction monitoring, paving the way toward integrated on‐chip biochemical analytics and multifunctional metasurface sensors.