Fig. 1. Schematics of metasurface sensor flow microchannel device. (a) Notched disc metasurface microfluidic device; (b) unit cell diagram of metasurface unit; (c) the top view of unit structure

Fig. 2. Formation of Fano resonance. (a) Comparison of transmission spectrum curves of symmetric and asymmetric structures (the line with dot marks represents complete silicon disk structure, and the line with square marks represents metasurface structure with notched disk); (b) the fitting curve model

Fig. 3. Normalized electromagnetic field distributions at each resonance under initial structure parameters. In the figures of field distributions, the white arrows represent the direction of the magnetic field vector, the black arrows represent the direction of the displacement current, and the color bars represent the amplitude of each field strength. (a)(c) Normalized electric field distribution |E/E₀| on the xoy plane and normalized magnetic field distributions |H/H₀| on the xoz and yoz planes at λ₁＝1219.95 nm; (d) schematic of electric quadrupole (EQ); (e)(g) normalized electric field distribution |E/E₀| on the xoy plane and normalized magnetic field distributions |H/H₀| on the xoz and yoz planes at λ₂＝1311.70 nm; (h) schematic of electric dipole (ED); (i)(k) normalized electric field distribution |E/E₀| on the xoy plane and normalized magnetic field distributions |H/H₀| on the xoz and yoz planes at λ₃＝1527.55 nm; (l) schematic of magnetic dipole (MD)

Fig. 4. Influences of structural parameters on sensing characteristics. (a) Influence of rectangular notch length l on resonance peak; (b) influence of rectangular notch width g on resonance peak; (c) influence of period P on resonance peak; (d) influence of silicon disk’s radius R on resonance peak; (e) influence of silicon disk’s thickness t on resonance peak

Fig. 5. Microfluidic sensing detection. (a) Influence of analyte thickness on Fano resonance peak; (b) transmission spectrum change of solution to be tested with different refractive indexes; (c) refractive index sensitivity of different resonances