## 4 Results and Discussion
Because the real component of the propagation constant \(\beta_{v}\) for isopropyl alcohol is smaller (\(\beta_{v}=4.2+i\cdot 104.321\)) than the imaginary component, abnormal modes will be generated in slits; the EM image of these modes shows a similar behavior to the case of air in the slits. The amplitude of the signal is smaller and has a central maximum that is more flat (Figure 5b). This gives new ways for MSGs in sub-subwavelength regime to be used as sensors (as biosensors using evanescent modes generated space between strips and extremely low frequency plasmons). In order to obtain a silver strip with different widths and thickness in the range of micrometers, different masks/stencils with different microstrip widths were used. Once a metal coating has been applied to a surface, it is critical to determine the adhesion properties of the deposit. In the case of an MSG made from silver strip having 14 \(\upmu\)m thickness, the width of strips where \(x_{c}=1.2\) mm and the width of slits is \(x_{d}=0.8\) mm is analyzed, considering that the wavelength of incident field is \(\lambda=0.6\) m (corresponding to a 500 MHz frequency). A region of 16 \(\times\) 16 mm\({}^{2}\) from MSG has been scanned with 0.1-mm steps in both directions. The scanning along the \(x\) direction was done to correspond with a few periods of gratings, \(x_{0}=x_{c}+x_{d}\). The working frequency was 476 MHz. For MSG excitation with EM field TM\({}_{x}\) polarized, the simulation was performed using XFDTD 6.3 software produced by REMCOM (State College, PA, USA) [86]. According to Ref. [79], the value of dielectric permittivity of silver is \(\varepsilon_{m}=-48.8+j\cdot 3.16\). Figure 6 shows the dependency of e.m.f. amplitude induced in the reception coil of a sensor on the scanning of the MSG taken into study, the image showing that this type of sensor correctly relies on conductive strips with 14 \(\upmu\)m thickness and eventual non-adherence to support and/or interruptions. These results are in good concordance with theoretical estimations. They confirm a good adhesion of the silver paste on polyimide, as well as good alignment of the strips. It is known that the biosensing characteristic is strongly dependent on the deposition condition, which affects the physical properties of the thin film. Using the procedure and sensor described earlier for eNDE of MSG, interruption of a strip stopped the propagation of evanescent waves in the nearest slit so that the amplitude of e.m.f induced in the reception coil practically decreased to zero when the aperture's sensor was in the corresponding region of the slit. The roughness feature is emphasized by the propagation of surface polaritons [29]. Figure 6: Amplitude of e.m.f. induced in the reception coil at the scanning of silver strip grating. For the second type of material taken into study (FRPC), the EM behavior of the composite was simulated by FDTD software; the samples were CAD designed following textiles features, and compared with eNDE tests. One cell of woven carbon fiber has been designed in the TexGenTextile Geometric modeler software (University of Nottingham, Nottingham, UK) (Figure 7a) and exported in CAD format in order to be used in FDTD software (XFDTD REMCOM, State College, PA, USA). The 5 \(\times\) 5 rows were represented in different colors in order to easily follow their intersection when woven. The cell dimension in FDTD simulation is 0.04 mm, and the grid size is 146 \(\times\) 146 \(\times\) 45 cells. The perfectly matched layer boundary condition was applied at the grid boundaries. The result of the simulation presented in Figure 7b is a snapshot from a field sequence, showing the \(H_{y}\) field progress at a particular slice of the geometry. In this case, the role of conductive strips is taken by carbon fibers, which act as MSG [71]; the apparition of evanescent waves can also be emphasized.