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Opt Quant Electron (2017) 49:320 DOI 10.1007/s11082-017-1147-8 Design and simulation of a flexible and ultra-sensitive biosensor based on frequency selective surface in the microwave range Hamed Emami-Nejad1 • Ali Mir1 Received: 5 June 2017 / Accepted: 21 August 2017 Ó Springer Science+Business Media, LLC 2017 Abstract In this paper, we present design and simulation of a very high sensitive biosensor based on frequency selective surface metamaterial for cancerous cells detection, in the GHz range. Split-ring resonators are used in the proposed biosensor structure because of their high sensitivities to electromagnetic waves. We have used the Cole–Cole parameters of ex vivo normal, malignant and cirrhotic cells, to do our device simulations by using Debye model. Its resolution is approximately 50 GHz, with very fine ability to separate the cancer cell types. Important advantages of our proposed biosensor are freelabel, low-cost manufacturing as much as photonic crystal sensors, detection of biomolecular composition and ultra-sensitivity. Also it can be produced locally. Keywords Biosensor  Cancerous cells  Frequency selective surface  Debye model  Split-ring resonator 1 Introduction Metamaterials (MM) are periodic combinations of subwavelength resonant structures which appear to have special frequency dependent bulk material characteristics. An array of MM resonators on a substrate is also known as metasurface or planar MM and can be measured in a THz-spectroscopy setup in transmission and reflection. Like the metal hole array (MHA) it has resonant characteristics regarding impinging electromagnetic waves. But unlike the MHA the resonators are flat in terms of wavelength, so that the resonant frequency is depending on the surrounding materials’ refractive indexes. Therefore the shape of the resonance will hardly change when the resonant frequency is shifted due to dielectric loading on one side of the resonators only (Debus 2013). Frequency selective surfaces (FSSs) have been around a long time, easily over 50 years if not longer. Probably & Ali Mir mir.a@lu.ac.ir 1 Electronic Group, Faculty of Engineering, Lorestan University, Khorramabad, Iran 123 320 Page 2 of 15 H. Emami-Nejad, A. Mir the best introduction and practical design guide is by Ben Munk which contains some history (Munk 2000). For those interested in computational methods, an early review by Mittra et al. (1988) is recommended. Using of bio-electromagnetic sensors is of great interest in many application fields, such as medicine, microbiology, physics, environmental and personal safety. Sensors suitable for biomedical applications (e.g. to measure molecular concentrations, investigate the DNA, estimate the pH, etc.) are characterized by specific performance requirements (Raghavan and Rajeshkumar 2013). Cancer is the uncontrolled growth of abnormal cells in the body, called as malignant cells. By developing microwave devices and combining it with structures inspired by MMs, it can lead to a very cost-effective device that can localize with high precision an abnormality within the human body. The basic principle behind the cancer detection is, a small change in the water content of biological tissues creates changes in the magnitude of the permittivity, e, and conductivity, r, of the tissues. By properly designing split ring resonators (SRRs) within a metamaterial, one can create materials with optical properties beyond the limitations of conventional, naturally occurring material or composites (Gadot et al. 2007; Ni et al. 2013). This has been demonstrated in microwave, infrared, and terahertz regions. In physics, Microwave radiation are a form of electromagnetic radiation with wavelengths ranging from 1 m to 1 mm; with frequencies between 300 MHz and 300 GHz (Jones et al. 2007). An electromagnetic source generates an electromagnetic wave impinging on the without any material under test has a specific MM array and a detector is placed to reveal the signal after the array. The variation of the permittivity caused by the presence of the material under test, acts on the capacitance of the resonators, leading to a high-sensitive variation of the sensor resonant frequency. Thus the shift in resonance frequency and the shape of the response is extremely useful to detect the tumor (Chen et al. 2012). Recently, biosensing technologies based on metamaterials have attracted significant attentions from the microwave to optical frequency because of their cost-efficient and label-free biomolecule detection (Xu et al. 2011; Wu et al. 2013a, b, c). According to operating frequency of sensing biomolecule and component, the metamaterial based sensors are classified into three types: microwave biosensor, terahertz biosensor and plasmonic biosensor (La Spada and Bilotti 2011a). We proposed a GHz FSS device, made from symmetric SRRs of MM to sense small amounts of chemical and biochemical material. The proposed biosensor consists of an array of complementary metallic metamaterial resonators. The biosensor (without any material under test) has a specific resonant frequency. In Fig. 1 the sensing system operation pattern is shown. 2 Modeling of biosensor Proposed biosensor has ultra-sensitivity for detection of bio-molecular composition. The resolution of this biosensor is approximately equal to 1.25 GHz that can be increased with shrinking unit cell size, As a result our biosensor is flexible. Figure 2 shows the suggested biosensor structure made from FSS, which are periodic structures with a band pass frequency response. It will be shown; the proposed structure passes only the signals around the center frequency through the periodic complimentary SRR layer. 123