Tunable perfect metamaterial absorber design using the golden ratio and energy harvesting and sensor applications Emin Unal 1 • Furkan Dincer 2 • Erkan Tetik 3 • Muharrem Karaaslan 1 • Mehmet Bakir 1 • Cumali Sabah 4 Received: 13 June 2015 / Accepted: 14 August 2015 / Published online: 20 August 2015 Ó Springer Science+Business Media New York 2015 Abstract We present the design, characterization, theo- retical and experimental verification of a tunable perfect metamaterial absorber (MA) based electromagnetic (EM) energy harvesting and sensor application. We have used the golden ratio while determining the dimensions allowing a simple configuration and an easy fabrication for the pro- posed structure. We have examined and analyzed the per- fect absorption (both numerically and experimentally) and EM energy harvesting (numerically) behaviors of the pro- posed structure in order to verify and show the character- istics of the model. It is shown that 99.9 % maximum absorption rate is achieved at 6.78 GHz, and MA structure can be used as an EM energy collector. In order to support the numerical study, an experimental study is realized. We have then developed a sensor application of the proposed MA structure and observed the effects of the harvesting system. Perfect MA sensor based EM energy harvesting system is successfully achieved. 1 Introduction After the experimental study on metamaterials (MTMs) was initially introduced in 2000s [1, 2], the researches in meta- materials have rapidly expanded and created a great interest in science and technology communities. MTMs which are defined as artificial electromagnetic (EM) structures, are represented by the controllable effective EM parameters described as permittivity e (x) and permeability l (x) pro- viding unusual features not easily available in nature. With the increase of research on materials, researchers have begun to focus on MTM studies including their fabrication meth- ods and applications, such as sensing [3], sensor [4–6], superlens [7], EM cloaking [8, 9] and so on [19–21]. In researches conducted in recent years, it is seen that MTMs can be used as a base for perfect absorbers [10–18] which can be easily implemented in many important applications because it shows a great absorptivity even at terahertz fre- quencies. Another concept of MTM researches is the EM energy harvesting applications, one of which was focused on a specific type of split ring resonator (SRR) for an EM energy harvesting application [22, 23]. It shows in this study that MTMs are also compatible with other functional applications including EM energy harvesting. Nowadays, it is known that the energy harvesting devices can harvest many types of energies, for example, acoustic or EM energy which can be converted to alternating (AC) or direct (DC) current signal by using common converting techniques [24]. These energy harvesting devices consist of structural sys- tems converting the energy from one form to another. In this regard, MTMs can be designed to convert different energy types because of their structural properties and used in the energy harvesting devices. In addition, if the metamaterial absorber (MA) structures are used in the energy harvesting, harvesting systems having different characteristics for the & Cumali Sabah sabah@metu.edu.tr 1 Department of Electrical and Electronics Engineering, Iskenderun Technical University, Iskenderun, Hatay 31200, Turkey 2 Department of Electrical and Electronics Engineering, Kilis 7 Aralik University, Kilis 79000, Turkey 3 Information Technology Department, Usak University, Usak 64100, Turkey 4 Department of Electrical and Electronics Engineering, Middle East Technical University-Northern Cyprus Campus, Kalkanli, Guzelyurt, TRNC/Mersin 10 99738, Turkey 123 J Mater Sci: Mater Electron (2015) 26:9735–9740 DOI 10.1007/s10854-015-3642-7