Fig. 1. Structural diagram of proposed sensor. (a) Lateral view of sensor; (b) unit cell of the metamaterials-based sensor's cap

Fig. 2. Dispersion curves of ethanol-water mixtures with different mole fractions of ethanol. (a) Real part of permittivity; (b) imaginary part of permittivity; (c) refractive index; (d) absorbance

Fig. 3. Electromagnetic response of sensor. (a) Reflection spectrum of sensor; (b) surface current distributions at different resonant dips; (c) electric field lines at resonant dip B; (d) electric field intensity distribution at resonant dip B

Fig. 4. Reflection spectra and sensitivity of sensor. (a) Simulated reflection spectra of sensor when refractive index of dielectric in microfluidic channel changes; (b) resonant frequency of each reflection dip in reflection spectra versus refractive index of dielectric in microfluidic channel; (c) sensitivity of each reflection dip in reflection spectra

Fig. 5. Calibration of sensor. (a) Reflection spectra of sensor filled with ethanol-water mixtures under different mole fractions of ethanol; (b) resonant frequency of sensor versus ethanol mole fraction; (c) reflectivity at resonant dips of sensor versus ethanol mole fraction

Fig. 6. Predicted ethanol mole fraction and error by sensor. (a) Predicted ethanol mole fraction;(b) error between predicted ethanol mole fraction and real one