Scalable Fabrication of Thermally Reconfigurable Ge Metasurfaces Using Stencil Lithography for Mid‐Infrared Molecular Fingerprinting

Surface‐enhanced infrared absorbance spectroscopy (SEIRAS) enables sensitive, label‐free molecular detection on compact platforms, but practical deployment is hindered by low‐throughput fabrication and limited bandwidth of photonic resonators. Here, we present a scalable stencil lithography approach for fabricating large‐area Ge pillar metasurface arrays supporting polarization‐insensitive Mie resonances. We leverage a combined geometric and thermal resonance tuning approach where geometric scaling yields discrete resonances spanning the 950–1700 cm − 1 molecular fingerprint region and thermal modulation of Ge's refractive index enables post‐fabrication dynamic tuning of these discrete resonances at a rate of ∼0.18 cm − 1 K − 1 across 300–500 K. This combined resonance sweeping enables controlled molecular‐photonic mode alignment at the same location, a critical requirement for SEIRAS. We reconstructed PMMA thin‐film vibrational signatures across 1100–1215 cm − 1 and detected polystyrene microparticles, resolving modes near 1450 and 1492 cm − 1 . This platform combines scalable fabrication, broad spectral coverage, and dynamic resonance tuning for mid‐IR molecular fingerprinting with potential applications in polymer and microplastic detection.