Highly sensitive detection of 4-mercaptohydrocinnamic acid proportion using terahertz metamaterial

Metamaterials are artificial materials with unique electromagnetic properties and could exhibit a strong electromagnetic resonance. Resonant metamaterials are widely used in the field of biosensors because they are sensitive to the changes of surface dielectric environment. In this study, we demonstrated a highly sensitive detection method of 4-Mercaptohydrocinnamic acid using terahertz metamaterials fabricated on silicon substrate with metal arrays of the three bars structure. We measured the transmission spectra of the metamaterial to detect the 4-Mercaptohydrocinnamic acid at three different densities by the terahertz time-domain spectroscopy system. With the density of 4-Mercaptohydrocinnamic acid increasing, resonance dips exhibit the red-shift phenomena and transmission at the resonance frequency simultaneously reduce. The movement of resonance dips and the change of transmission show that the three bars resonators are sensitive to the density of analyte. The finite-difference time-domain simulation shows a good agreement with the experimental data, and the simulation of surface current and electric field distributions at resonance dips can further understand the resonance modes in transmission spectra. Our study provides new prospect into the application of terahertz metamaterials in biosensing.