## 1 Introduction
Science 2009, 325, 1513–1515]. Reprinted with permission from AAAS [8]; (**e**) metal-dielectric layered metamaterial composed of coupled plasmonic waveguides Reproduced from [[PERSON] et al. Experimental realization of epsilon-near-zero metamaterial slabs with metal-dielectric multilayers. Appl. Phys. Lett. 2013, 103, 051111], with the permission of AIP Publishing [9]; (**f**) Split ring resonators (SRRs) oriented in all three dimensions. Reproduced from [[PERSON] et al. Acoustic band gaps of three-dimensional periodic polymer cellular solids with cubic symmetry. Appl. Phys. Lett. 2013, 114, 043521], with the permission of AIP Publishing [10]; (**g**) wide-angle visible negative-index metamaterial based on a coaxial design. From [[PERSON] et al. Optical Metamaterials—More Bulky and Less Lossy. Science 2010, 330, 1633–1634]. Reprinted with permission from [PERSON] [7]; (**h**) connected cubic-symmetry negative-index metamaterial. Reproduced with permission from [[PERSON] et al. ], [Nanoscale]; published by [Royal Society of Chemistry], [2016] [11]; (**i**) metal cluster-of-clusters visible-frequency magnetic metamaterial. Reproduced with permission from [[PERSON], [PERSON] et al. ], [Adv. Mater. ]; published by [[PERSON]], [2011] [12]; (**j**) negative-index metamaterial composed of two sets of high-refractive-index dielectric spheres arranged on a simple cubic lattice. NRI, negative refractive index. Reproduced with permission from [[PERSON], [PERSON] et al. ], [Adv. Mater. ]; published by [[PERSON]], [2011] [12]. respectively, 82%, 67% and 93% [1]. In 2013, [PERSON] et al. introduced a rectangular \"U-shaped\" left-handed metamaterial for several orthogonal array structure, and the effective medium ratio was 1.99 [16]. In 2014, [PERSON] et al. proposed a 30 \(\times\) 30-mm\({}^{2}\) \"H-shaped\" metamaterial for multi-band operations, and the resonance frequencies were found at S-, C-, X- and Ku-bands. In addition, the H-shaped structure exhibited double-negative characteristics, but the effective medium ratio was 3.64. However, the sensitivity of these metamaterial was only 13 [17]. In 2015, [PERSON] et al. explained a \"ring-shaped\" metamaterial structure applicable as a filter in waveguides. Moreover, the effect on the resonance of the parameters, such as the ring width, inner and outer ring gap, splitting of the ring, substrate material thickness and orientation of the substrate material, was investigated in their paper [3]. In 2015, [PERSON] et al. introduced a two \"G-shaped\" double negative (DNG) metamaterial, where the unit cell and arrays are different in size, and the metamaterial was suitable for S- and C-band applications. The dimensions of the presented metamaterial structure were 12 \(\times\) 12 mm\({}^{2}\)[18]. In 2015, [PERSON] et al. proposed a metamaterial based on split ring resonators to produce a negative refractive index at terahertz frequencies. The 2200 \(\times\) 2200-nm\({}^{2}\) structure exhibited left-handed characteristics at approximately 9.7 THz [2]. In 2016, [PERSON] et al. designed an 8.5 \(\times\) 8.5-mm\({}^{2}\) \"double Z-shaped\" left-handed metamaterial via coplanar electric and magnetic resonators, and the effective medium ratio was 4.80. The resonator structure was composed of two orthogonal Z-shaped metal strips, and the metamaterial exhibited resonance at 7.3, 8.1 and 9.4 GHz [19]. In 2015, [PERSON] et al. suggested an 8 \(\times\) 8-mm\({}^{2}\) \"hexagonal\" DNG metamaterial, where the bandwidth was 1.75 GHz (from 1.68-3.43 GHz) and 0.96 GHz (from 5.04-6.0 GHz) [4]. In 2016, [PERSON] et al. demonstrated a \"ring-shaped\" 5 \(\times\) 5-mm\({}^{2}\) meta-atom for wearable, flexible and stretchable microwave meta-skin, with clocking effects from 8-13 GHz and an effective medium ratio of six [5]. In 2016, [PERSON] et al. presented a left-handed metamaterial created by the combination of ferrite sheets and dielectric rods to investigate the electromagnetic properties for X-band applications [20]. In 2016. [PERSON] et al.