Figure 1. Fabrication and characterization of a metamaterial sensor device integrated with microfluidics.

a, A schematic representation of the fabricated miniaturized GC-HMM sensor device with a fluid flow channel and a SEM image of the fabricated 2D subwavelength gold diffraction grating on top of the HMM with an average period of 500 nm and hole size of 160 nm (scale bar, 2 μm). b, Photograph of the GC-HMM sensor device fully integrated with a microfluidic channel and sample tubing. Scale bar, 10 mm. c, Real parts of effective permittivity of gold/Al₂O₃ HMM determined using effective media theory, which shows a hyperbolic dispersion at λ≥520 nm (dashed vertical line). The experimentally obtained permittivity values of gold and Al₂O₃ were used in these calculations. The fabricated eight pairs of gold/Al₂O₃ HMMs are shown in the inset. d, Reflectance spectra of the GC-HMM at different angles of incidence. The GC-HMM sample shows four prominent reflectance dips, corresponding to the bulk plasmon polariton modes, and two weak reflectance minima in the shorter wavelengths, corresponding to the SPP modes. A blue shift in resonance wavelength with increasing angle of incidence shows all six modes are guided modes.