Solid analyte and aqueous solutions sensing based on a flexible terahertz dual-band metamaterial absorber

A high-sensitivity sensing technique was demonstrated based on a flexible terahertz dual-band metamaterial absorber. The absorber has two perfect absorption peaks, one with a fundamental resonance (f(1)) of the structure and another with a high-order resonance (f(2)) originating from the interactions of adjacent unit cells. The quality factor (Q) and figure of merit of f(2) are 6 and 14 times larger than that of f(1), respectively. For the solid analyte, the changes in resonance frequency are monitored upon variation of analyte thickness and index; a linear relation between the amplitude absorption with the analyte thickness is achieved for f(2). The sensitivity (S) is 31.2% refractive index units (RIU-1) for f(2) and 13.7% RIU-1 for f(1). For the aqueous solutions, the amplitude of absorption decreases linearly with increasing the dielectric constant for the ethanol-water mixture of f(1). These results show that the designed absorber cannot only identify a solid analyte but also characterize aqueous solutions through the frequency shift and amplitude absorption. Therefore, the proposed absorber is promising for future applications in high-sensitivity monitoring biomolecular, chemical, ecological water systems, and aqueous biosystems. (c) The Authors.