## 3 Experiments and Results  
To experimentally verify the functionality of the proposed cross-meandering resonator, the structure is etched in a 1 mm thick copper film using wire electrical discharge machining (WEDM). Figure 4a shows a photograph of the fabricated sample. The overall size of the sample is about 164 mm \(\times\) 164 mm (\(\sim\)0.49\(\lambda_{0}\)\(\times\) 0.49\(\lambda_{0}\)). A detailed size comparison can be seen in Table S1 of the Supplementary Materials. A zoomed-in view of the resonator is displayed in Figure 4b. The measured geometrical parameters of the resonator are as follows: \(w\) = 28.95 mm, \(l\) = 14.95 mm, \(a\) = 0.95 mm, \(b\) = 1.05 mm. To test the shielding efficiency and wireless signal transmission of the sample, we customized an open side shielding box and a rolled-up lid, as depicted in Figure 4c.d. Here, the box and lid are made of permalloy, due to its high permeability at the power frequency, and the thicknesses are both 1 mm. The dimensions of the shielding box and lid are \(m\) = \(h\) = \(n\) = 160 mm, \(e\) = 10 mm. Figure 4: **(a)** Photograph of the cross-meandering resonator sample. **(b)** Zoomed-in view of the resonator. **(c)** Shielding box made of permalloy. The length, width and height of the shielding box are represented by \(m\), \(n\) and \(h\) respectively. **(d)** Shielding box and lid made of permalloy. The width of the curled edge of the lid is represented by \(e\). Figure 3: **(a)** Electric field (\(1E1\)) and **(b)** magnetic field (\(1H1\)) distributions when the material of the resonator layer is copper (white fonts). The “wire” and “cubic box” refer to the positions where the wire and cubic box are located in the simulation calculation. **(c)** Calculated ratios of \(1E1^{2}\) and \(1H1^{2}\) at the resonator layer composed of copper. **(d)** Electric field (\(1E1\)) and **(e)** magnetic field (\(1H1\)) distributions when the material of the resonator layer is permalloy (white fonts). **(f)** Calculated ratios of \(1E1^{2}\) and \(1H1^{2}\) at the resonator layer composed of permalloy. To measure the power frequency electric field intensity, a MEMS AC/DC electric field sensor (JDC-W01) was brought from Beijing Zhongke Feilong Sensing Technology Company Limited (Beijing, China). In the experiment, the electric field sensor was supported in the open-sided shielding box by a stack of sticky notes, as shown in Figure 5a. An electric wire was used as the emission source of power frequency (50 Hz) electromagnetic field. When the whole device was in an open environment (Figure 5b), we measured electric field intensities, which changed with the change of the distance between the electric wire and sensor, as are displayed by the black dots in Figure 5c. The red line in Figure 5c is a fitting curve based on the equation \(I=I_{0}+Ae^{-D/I}\), where \(I\) and \(D\) represent the intensity and distance, respectively. The fitting coefficients are \(I_{0}=-0.005\), \(A=0.491\), and \(t=14.948\). This indicates that the electric field intensity decreases exponentially with the distance. Then, the permalloy lid and cross-meandering resonator sample were tightly connected with the cubic box. To achieve good electrical contact, we first pasted the box and resonator surface together with an electromagnetic shielding sealing strip, and then covered the joint with a conductive cloth tape. In the follow-up experiments, we put the electric wire close to the permalloy lid and cross-meandering resonator sample, as shown in Figure 5d,e. Table 1 shows the results of multiple measurements in three conditions. It is obviously observed that the cross-meandering resonator sample and the permalloy lid both effectively block the transmission of a power frequency electromagnetic field, because the electric field intensity in the shielding box is less than the minimum that the sensor can measure (10 V/m).