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 (R2 > 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.