A Metamaterial-Based Absorber for Liquid Sensing in Terahertz Regime

A metamaterial (MM) absorber and its application in liquid sensing are proposed in this article. The unit cell of the sensor structure consists of two quartz substrates with metallic patterns and sheets printed on their surfaces. The liquid tunnel with optimal thickness is created by placing the glass micro-pearls between the quartz substrates. By incorporating dual semitoroidal resonators, the enhanced spectral shift per refractive index unit (RIU) improves the sensitivity of the proposed design effectively, and sensitive frequency detection with 52.50 GHz/RIU is numerically demonstrated. Moreover, we experimentally demonstrate its application for determining ethanol and sucrose solutions with different concentrations and three commonly used oils. A good agreement with the experiments and simulations is obtained. In addition, the proposed sensor has the advantages such as compact size, easy fabrication, and reusability, which offers excellent potential in food industry applications.