Morphological, optical, and electrical properties of CoxCa(0.90-x)Ni0.10Fe2O4 based flexible metamaterial substrate for industrial chemical contamination sensing

Abstract

State-of-the art research on conventional microwave substrates reveals limitations of restricted flexibility, poor adaptability to irregular surfaces, and reduced effectiveness in complex sensing environments, leading to the development of a flexible microwave substrate using Co–Ca ferrite for feasible applications in detecting industrial chemicals. In this paper, CoxCa (0.90-x) Ni0.10Fe2O4 (x = 0.25, 0.50, and 0.75) based flexible substrate is developed through the sol-gel method, and a rectangular enclosed cross-dumbbells (RECD) metamaterial structure is designed for industrial chemical contamination sensing. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to morphological analysis of the nanoparticles of the substrate. XRD patterns shows the presence of crystalline phases, which facilitate the determination of strain within these materials. FESEM images demonstrate a structural composition characterized by nanosized grains and capillary-nanopores, where these nanosized grains are found uniformly distributed across the film's surface and results structural homogeneity. The synthesized nanoparticles are employed as a solid substrate utilizing PVA (polyvinyl alcohol) to ensure a uniform structure. The dielectric constant of the developed substrate is measured using the DAK 3.5 dielectric measurement kit, and it shows dielectric permittivity values ranging from 1.77 to 3.32 with loss tangents ranging from 0.031170 to 0.1929 for x = 25 % to x = 75 %. Metamaterial characteristics of the fabricated RECD structure on Co–Ca ferrite is analysed and μ-negative characteristics is achieved from 4.7 GHz to 6 GHz. Additionally, the reflection coefficient of the RECD metamaterial is also investigated for different bending condition up to an angle of 30ο. The simulated and measured S21 results strongly match each other. The sensing performance is evaluated for three concentrations of methanol and ethanol, demonstrating excellent contamination sensing capabilities with sequential frequency shifting. This study undoubtedly revealed that Co–Ca ferrite-based flexible metamaterial have great potential for high performance industrial chemical contamination sensing applications.

Keywords

• Flexible metamaterial
• Sol-gel method
• Microwave sensing
• Chemical sensing
• Chemical contamination