Reconfigurable Nanogap SERS for Multiscale Molecular Sensing on Curved Surfaces

Surface-enhanced Raman scattering (SERS) offers ultrasensitive molecular fingerprinting, yet most current substrates rely on static architectures with fixed nanostructures, which undermines their quantitative reliability and prevents conformal sensing. Here, we introduce a reconfigurable and conformable SERS platform based on Au-coated shape memory polymer (SMP) nanopillar arrays that reversibly switch out-of-plane (vertical) Au─Au nanogaps. The substrate comprises Au-coated SMP nanopillars embedded with silver nanoparticles (AgNPs) that serve as photothermal triggers and mechanical reinforcements. Compression and laser-induced recovery of the nanopillars reversibly modulate the vertical Au─Au nanogaps from wide to narrow states, thereby tuning near-field coupling, hotspot density, and molecular accessibility. This reversible out-of-plane reconfiguration enables the same platform to support detection of analytes across different size scales. The size-adaptive sensing capability is demonstrated by the detection of a macromolecule (hemoglobin, 64 kDa) on curved stainless-steel surfaces in the wide-gap state and of a small molecule (thiram, 0.24 kDa) on fruit surfaces in the narrow-gap state. The platform also maintains performance over repeated compression-recovery and washing-measurement cycles, confirming reusability and operational stability. Overall, this adaptive nanogap-switching strategy offers a practical route toward reusable, size-adaptive SERS platforms for next-generation food safety and forensic chemical analysis.