Square split enclosed by staircase-shaped metamaterial absorber for oil sensing applications

This paper presents a staircase-shaped microwave metamaterial sensor designed for accurate oil detection in the S and C frequency bands. The sensor shows very high absorption, reaching 99.91 % at 3.6 GHz and 99.74 % at 5 GHz, and maintains stable performance even when the incident wave angle changes up to 180°. It is compact, with a unit cell size of only 0.144λ × 0.144λ, and has a high effective medium ratio (EMR) of 6.94. The sensor also demonstrates unique electromagnetic properties such as near-zero permittivity, permeability, and refractive index, along with single-negative behavior. An equivalent RLC circuit was developed in ADS software to verify its radio-frequency characteristics, and the results matched well with simulations. The sensor achieved a sensitivity of 2.59, a quality factor of 26.604, and a figure of merit of 43.19, proving its accuracy and reliability. Thanks to its low cost, high sensitivity, and wide usability, this sensor is a strong candidate for applications such as liquid detection, oil sensing, and microfluidic sensing. • Staircase-shaped microwave metamaterial sensor for high-sensitivity oil detection. • Achieves remarkable peak absorption rates of 99.91 % at 3.6 GHz and 99.74 % at 5 GHz. • The sensor's high EMR of 6.94 enhances its exceptional performance in oil sensing. • The 12 mm × 12 mm sensor with a 0.144λ unit cell suits space-constrained applications. • The sensor's 2.59 sensitivity and 26.604 Q-factor enable precise oil sample detection. • The absorber shows near-zero permittivity, permeability, refractive index, and SNG. • Demonstrating stable performance across incident wave angles up to 180°.