Strain-Regulated Plasmonic Excitation and Raman Scattering for Tunable Surface-Enhanced Raman Scattering in a...

Flexible plasmonic substrates are attractive for conformal and in situ surface-enhanced Raman scattering (SERS) detection; however, gap-free metallic nanostructures have received limited attention for strain-tunable SERS despite their facile fabrication and spectral tunability. This paper reports a stretchable Ag grating on a sinusoidal polydimethylsiloxane (PDMS) substrate that enables strain-regulated modulation of plasmonic response and Raman scattering. Strain applied perpendicular (εx) and parallel (εy) to the grating lines induces distinct morphological changes, leading to opposite spectral shifts relative to the 532 nm excitation wavelength. Under longitudinal stretching, the local-field enhancement exhibits a nonmonotonic dependence on strain and reaches its maximum at εy = 10%, although the plasmon resonance further blueshifts toward the excitation wavelength at larger strains. Electromagnetic simulations and Purcell-factor analysis reveal that stretching simultaneously regulates excitation-field enhancement and plasmon-mediated Raman scattering. This excitation-scattering modulation produces the strongest SERS response for crystal violet at εy = 10%, enabling a detection limit of 10-11 mol/L. Moreover, the substrate maintains high reproducibility, with an RSD = 4.5% over 60 stretching cycles, highlighting its potential for mechanically tunable and flexible molecular sensing.