Sensitive Metamaterial Sensor for Distinction of Authentic and Inauthentic Fuel Samples MEHMET ALI TU ¨ MKAYA, 1 FURKAN DINC ¸ ER, 2 MUHARREM KARAASLAN, 1 and CUMALI SABAH 3,4,5 1.—Department of Electrical and Electronics Engineering, Iskenderun Technical University, Iskenderun, Turkey. 2.—Department of Electrical and Electronics Engineering, Kilis 7 Aralik University, Kilis, Turkey. 3.—Department of Electrical and Electronics Engineering, Middle East Technical University - Northern Cyprus Campus (METU-NCC), Kalkanli, Guzelyurt, TRNC/ Mersin 10, Turkey. 4.—Kalkanli Technology Valley (KALTEV), Middle East Technical University - Northern Cyprus Campus (METU-NCC), Kalkanlı, Gu ¨ zelyurt, TRNC/Mersin 10, Turkey. 5.—e-mail: sabah@metu.edu.tr A metamaterial-based sensor has been realized to distinguish authentic and inauthentic fuel samples in the microwave frequency regime. Unlike the many studies in literature on metamaterial-based sensor applications, this study focuses on a compact metamaterial-based sensor operating in the X-band frequency range. Firstly, electromagnetic properties of authentic and in- authentic fuel samples were obtained experimentally in a laboratory envi- ronment. Secondly, these experimental results were used to design and create a highly efficient metamaterial-based sensor with easy fabrication charac- teristics and simple design structure. The experimental results for the sensor were in good agreement with the numerical ones. The proposed sensor offers a more efficient design and can be used to detect fuel and multiple other liquids in various application fields from medical to military areas in several fre- quency regimes. Key words: Metamaterial, fuel sensor, gasoline, diesel INTRODUCTION Technology development now enables manufac- ture of different types of functional materials with extraordinary electromagnetic behavior. Such meta- materials (MTMs) cannot be readily found in Nature and are designed based on periodic struc- tures with distinct and specific properties such as negative refraction. The idea of materials having both negative dielectric constant and magnetic permeability at the same time was proposed theo- retically in 1968 by Veselago. 1 Unfortunately, that milestone study did not receive sufficient attention from the scientific community until its experimental verification by Pendry et al. in 1996 and 1999 2 and Smith et al. in the 2000s. During the last few years, many studies on different applications of MTMs such as cloaking, 3 superlenses, 4 antennas, 5 absor- bers, 6,7 and sensors 8 have been carried out. The benefits of MTMs have been used to design and manufacture highly efficient instruments, espe- cially for material sensing in different spectral ranges, from microwaves, terahertz, infrared, to optics. Materials considered for use in such sensor applications include solid dielectrics, 9–11 liq- uids, 12,13 and biomolecules 14–16 developed in the form of solid or liquid films. In this work, we realized another MTM sensor application. The proposed sensor enables applica- tions such as distinction of authentic and inauthen- tic fuel samples in the microwave frequency regime with higher efficiency. The resonator structure of the MTM is designed to enable measurements in the X-band frequency regime. The main purpose of the proposed MTM-based sensor structure is to distin- guish two fuel oil samples: one registered by a corporate company and the other not. We observed (Received October 7, 2016; accepted March 28, 2017) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-017-5485-x Ó 2017 The Minerals, Metals & Materials Society