The MIM metasurface with a polyimide insulator layer investigated here is schematically illustrated in Figure , along with a scanning electron microscopy (SEM) image of a fabricated structure. A key prerequisite for effective coupling between molecular vibrations and plasmonic modes is ensuring both a spectral and spatial overlap between them. A layered metamaterial arrangement used here, in which polyimide is wedged between a 50 nm thickness top nanodisk structure and an underlying 200 nm thickness metal reflector, is exceptionally well-suited in this respect, as it ensures that the resonant optical field is primarily confined in the insulator, as illustrated by the finite-difference time-domain (FDTD) simulation derived plots in Fig. . Conversely, the spectral overlap can be tuned by altering the scale of the metamaterial pattern, where nanodisk diameter D where changed in the 500 nm to 1600 nm range and period P was fixed at 1.5 × D.