Carbon nanotube-based flexible metamaterials for THz sensing

Metamaterials are carefully constructed materials, usually consisting of various periodically arranged subwavelength structures, that can manipulate electromagnetic waves in unique ways [1]. They can be used for a wide range of applications, including the formation of superlens [2], invisibility cloaks [3], strain sensors [4], pesticide sensors [5], etc. Thus, they have received a great deal of attention from the researchers in physics, materials science, optics, and chemistry 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.

Automated summary

Metamaterials are carefully designed materials that can manipulate electromagnetic waves in unique ways and have a wide range of applications. Carbon nanotube-based materials show advantages for flexible terahertz metamaterials. A flexible terahertz metamaterial sensor based on a subwavelength periodic array structure of carbon nanotube thin films was reported, showing enhanced resonance transmission peaks and adjustable resonant frequency and amplitude modulation under small external strains. The materials and device strategies developed in this research will help in developing new terahertz functional devices.