Carbon nanotube-based flexible metamaterials for THz sensing

The inherent limitations of metal-based metamaterials are the key factors limiting the rapid development of the field of flexible terahertz metamaterials. The advantages of carbon nanotube-based materials and devices in terms of weight, cost, and flexibility of free bending, make them of great use for flexible terahertz metamaterials and devices. Here, a flexible terahertz metamaterial sensor, based on a subwavelength periodic array structure of carbon nanotube thin films, is reported. The proposed flexible metamaterial can achieve the surface plasmon resonance to generate local field enhancement phenomenon, resulting in enhanced resonance transmission peaks. We observed that the resonant frequency and amplitude modulation can be continuously adjusted when the device is subjected to a small external strain. In addition, we found that the terahertz transmission spectrum changes significantly when analytes or dielectric layers, with different refractive indices, thicknesses, or carrying pore defects, are added on the surface of the carbon nanotubes film or below the polyimide substrate of the flexible metamaterials sensor in the bent state. Our results show that these materials and designed device strategies will aid in developing new terahertz functional devices, such as strain sensors, biochemical sensors, curved surface defect detectors, and wearable terahertz imagers.