Anticorrosive Multi-band 5G Wireless Communication and THz Electromagnetic-Interference Shielding with Graphene Assembled Film


 Since first developed, the conducting materials in wireless communication and electromagnetic interference (EMI) shielding devices have been primarily made of metal-based structures. Here, we present a highly conductive and corrosion-resistant graphene assembled film (GAF) that can be used to fabricate multi-band 5G wireless communication electronics and EMI protection at frequencies ranging from tens of MHz to THz to demonstrate its potential in metal replacement in practical electronics. The GAF based antennas (dipole antenna, ultra-wideband antenna and 5G wireless communication antenna array) are comparable with metal-based antennas in terms of performance and device complexity. The EMI shielding effectiveness of GAF can reach up to 127 dB in the frequency range of 2.6 GHz - 0.32 THz, and a maximum shielding effectiveness per unit thickness is of 6966 dB/mm. Furthermore, the GAF metamaterials exhibit promising frequency selection characteristics and angular stability as flexible frequency selective surfaces that can work at 3.5 GHz and 60 GHz respectively.


Introduction
The matured development of 5G and emerging 6G wireless communication electronics (WCE) has the potential to revolutionise many applications such as healthcare 1 , tness monitoring 2 , wearable communication 3,4 , Internet of Things 5 , e-skins 6,7 , and so on, making our lives more convenient, safe and productive. To e ciently transport electrical signals and electromagnetic waves at multi commnunicaton bands, the 5G and 6G networks require more antennas, much larger bandwidths, and a higher density of base stations than previous generations of communication networks. As a result, the demand for WCE will skyrocket in the approaching years: for example, the number of global 5G base stations is expected to reach 65 million by 2025 8 . Together with the explosive growth of WCE devices, particularly mobile terminals, serious issues of electromagnetic interference (EMI) have also arisen, which can lead to signal loss, data misinterpretation, and even system failure 9 . The increased electromagnetic pollution can also be hazardous to human health 10 .
In general, the electrical conducting component in WCE devices and effective EMI shielding materials require high electrical conductivity as well as high electron mobility 11 . Metals have such characteristics (with electrical conductivity of over 10 7 S/m and electron mobility of 10 -50 cm 2 /V·s) 12 , so previous WCE devices and EMI shielding materials have conventionally been made from metal-based structures for decades 13,14 . However, with the growing demands for being exible and highly integratable, anticorrosive, lightweight, smaller in size, easy-to-fabricate, and operating at higher frequency communication bands (from dozens of GHz to THz), the metal material based structures are beginning to show less ability to coupe with next generation WCE and EMI shiledling requirements 15 . In addition, due to the pollutants and CO 2 emission generated during metal mining and manufacturing processes 16 , sustainable development in the next generation consumer electronics becoming essential due to the growing environmental impacts associated with the electronic waste (e-waste) 17 .
Metal free WCE devices and EMI shielding material are, however, challenging to make since it is hard to have a material simultaneously matching the high electrical conductivity and presenting good mechanical stability. In recent years, carbon based electronics, especially the possibility of exploiting graphene to assemble macroscopic structures has been demonstrated as a feasible approach to reach the target 18,19 . Previous research demonstrated that graphene can be directly grown, implanted or printed on a substrate to form a composite structure 20,21 . However, the conducting graphene layer in these structures typically has limited thickness or low coductivity, which results in high surface resistance and poor device performance 22,23 . Recent breakthroughs in the reduction of graphene oxide 24 and exfoliation of pristine graphene 25 have demonstrated that graphene assembled structures can reach electrical conductivities of up to 10 5 S/m [26][27][28] , and that such techniques can be applied in WCE 29,30 . Such electrical conductivity, however, is still two orders of magnitude lower than that of metal-based materials. Meanwhile, MXene, as a unique family of two-dimensional transition metal carbides and/or nitrides, can be used as an alternative materials to achieve this goal. MXene has a high electrical conductivity (around 10 5 S/m) and can provide effective electromagnetic shielding performance with low thicknesses 9,31 as well as be applied in WCE 32 . However, MXene are easily oxidised (unsuitable for long-term use) and di cult to produce in large quantities 33 , which limits its application in real-world commercial products.
Furthermore, so far, both graphene and MXene-based WCE devices and EMI shielding materials have only been demonstrated as concept validations with simple functions, no practical and advanced electronics have been designed or systematically compared with metal-based commercial devices in terms of robustness and device performance, etc. yet 34,35 .
Here, we report a scalable production of graphene assembled lm (GAF) with a conductivity of 2.58 × 10 6 S/m, and applied it in next generation WCE and EMI shielding materials. After 100,000 bending tests (with a bending radius of 1.5 mm), GAF lm can retain its high exibility and conductivity, with no structural damages. To investigate GAF's capabilities in 5G techonolgoy and exible electronics, we rst demonstrated its stable performance in 5G WCE as exible coplanar waveguide transmission lines and 1/4 wavelength resonators under various twisting conditions. GAF-based dipole antennas have a -39 dB re ection coe cient and a high gain of 1.89 dBi, which is comparable to copper-based antennas. and angular stability. Thus, our research demonstrates GAF's full potential as a sustainable alternative material in multi-band 5G communication electronics and EMI shielding for next-generation wireless communication electronics.

GAF Fabrication and Characterisation
To achieve graphene-based laminates with a high electrical conductivity, we introduce extremely large ake size graphene oxides (LGO) as the lm's building precursor to reduce the contribution of contact resistance. Fig. 1a is a schematic diagram of the fabrication process. The detailed fabrication procedures are described in Methods. With commercially standard equipment, GAF can be manufactured in a viable and scale manner, Supplementary Fig. 1-2 36 . Fig. 1b is a transmission electron microscope (TEM) image presents a typical LGO sheet with a lateral size of 108 μm. In the corresponding size distributions curve from optical microscope measurement, Fig. 1c, the average LGO lateral size is around 110 μm, which is signi cantly larger than any previously reported study 37,38 . To compare, lms made from typical size GO akes, Supplementary Fig. 3, have also been fabricated as a control experiment and been tested accordingly. GAF was manufactured by an optimised compression and secondary high temperature (2850˚C) graphitization process. The XRD (Fig. 1d) and Raman spectroscopy ( Fig. 1d and Supplementary   Fig. 4) con rm GAF's highly graphitized and defect free structure. Based on Raman measurement, a large crystallite size L a = 1967.95 nm in the GAF is also con rmed according to Equation 1 39 .
Small-angle x-ray scattering (SAXS) patterns of GAF, inserted in Fig. 1e, show a prismatic scattering pattern indicating GAF with highly aligned layered structure. In contrast, for typical ake size GO assembled lm (TGF), Supplementary Fig. 5, no such pattern is identi ed 40 . Supplementary Fig.6 is the top view GAF SEM image, microfolds are uniformly distributed on the GAF surface. As shown in Supplementary Fig. 7, the cross-section SEM images of the GAF characterise a thin lm with thickness of ~19 ± 0.5 μm. This thickness is similar to commercial copper foil applied in consumer electronic devices .
The electrical conductivity of all samples is measured by a four-probe method (Supplementary Fig. 8 and Supplementary Video 1). In Supplementary Fig. 9, the electrical conductivity of GAF and TGF fabricated under different conditions are characterized. The conductivity of GAF is 2.58 ± 0.06 × 10 6 S/m, which is 5 times higher than that of graphite lm (5×10 5 S/m) and about 2 times higher than HOPG (1×10 6 S/m) and TGF (9×10 5 S/m), as shown in Fig. 1e. In Supplementary Fig.10, the electron transfer pathway between GAF and TGF is proposed as the mechanism for this ultrahigh electrical conductivity 41 . 5G WCE are powered by radio frequency (RF) signal, for which skin depth effect cannot be negligible. To better integrate in 5G WCE electronics, the thickness of conducting material in the device always demands a thickness of around 20 μm or below. The skin depth can be calculated by the following Equation 2.
where f is the frequency, μ is the permeability and σ is the conductivity of conductive material. For nonmagnetic conducting materials, μ is taken as 4π×10 -7 N/A 2 . Taking the Radio Frequency Identi cation (RFID) communication frequency band (860 MHz) speci ed in EPC Gen2 standard as an example, to reduce the resistance loss, the thickness of conductive material should be greater than skin depth. Regarding this, in Fig. 1f, a selective area which requires materials having electrical conductivity higher than 0.75 × 10 6 S/m is identi ed. For non-metal materials, it can be found that among all novel developed materials, only graphene lms made by high temperature (over 2500 ℃) annealing can meet these requirements (Supplementary Fig. 11 and Supplementary Table 1-2,). Although metal materials, like gold (Au), silver (Ag), copper (Cu), aluminium (Al) and iron (Fe), has higher electrical conductivity, the apparent density of GAF (1.92 g/cm 3 ) is signi cantly lower, shown in Supplementary Fig. 12-13. In Fig. 1g and Supplementary Video 2, we demonstrate that GAF can retain its ultrahigh conductivity even after 100,000 bending cycles test with a bending radius of 1.5 mm. The SEM images show the durability of GAF that can endure a zigzag folding without any breakage ( Supplementary Fig. 14-15). A similar test was performed on a commercial copper foil with the thickness of 20 μm; the copper foil broke after only 12 folds (Supplementary Fig. 16).
To verify the excellent exibility of GAF electronics, a exible coplanar waveguide transmission line (FCPW TL) and a λ/4 short-circuited resonator based on silica gel lm ( Supplementary Fig. 17) are rst designed and fabricated. As shown in Fig. 1h-i, FCPW TL's transmission characteristics of the being bent and twisted at different conditions are investigated between the 10 MHz -12 GHz frequency band., It is found that bending and twisting has negligible effects on the transmission coe cient (|S 21 |) of GAF transmission line. Fig. 1j-k illustrate the |S 11 | (between 10 MHz to 12 GHz band) of GAF λ/4 short-circuit resonator in the original state and different twist states. Like GAF exible transmission line, the twist does not change the resonator's performance.

GAF as a Dipole Antenna and its Highly Anticorrosion Properties
A GAF dipole antenna is used in this study as an example to compare with metal antennas in terms of device performance and corrosion resistance, which is a continuing concern in next-generation WCE working at higher frequencies and operating powers. MHz, also indicating a matching performance with copper antenna. The measurement environments for the antennas are exhibited in Fig. 2f-g. In Fig. 2h, the GAF dipole antenna exhibits the highest gain of any graphene-based dipole antenna reported in the literature [42][43][44][45][46] . In supplementary Fig. 19, the E-eld distribution simulation results of the graphene dipole antenna in different phases indicates the current on the dipole arm is sinusoidally distributed.
The salt spray treatment is applied to the GAF and copper antennas to investigate their corrosion resistance, Supplementary Fig. 20. Fig. 2i-j are the digital photos of GAF antenna and copper anetnna after one week's and two weeks' salt spray: the copper antenna is rusted and then broken after the test, but the exterior of GAF antenna is unaffected. Fig. 2k illustrates the simulated and measured re ection coe cient |S 11 | at resonant frequencies of 865 MHz of the initial GAF antenna and after the salt spray treatments. The -10 dB bandwidth (BW) of the GAF antenna is from 790 MHz to 980 MHz, which covers the RFID communication frequency band. After salt spray treatment, the GAF's |S 11 | does not change.
However, the |S 11 | of copper antenna becomes only -6.25 dB at 865 MHz after two weeks of salt spray, Fig. 2l-m presents the measured gain at 865 MHz of GAF and copper antennas during the test, the gain of the GAF antenna is unchanged, but the copper antenna has a signi cantly lower gain of -2.74 dBi after two weeks of salt spray. This test con rms that, unlike metal based materials, because graphene is naturally more anticorrosive, no additional anti-corrosion coating is required in the GAF WCE to protect it from corrosion, which simpli es manufacturing and reduces weight.  47 . In this work, we con rm that GAF antennas can be used to directly replace metal-based antennas in commercial sub-6 GHz electronic devices, like mobile phone and drone, without losing functionality, as shown in Fig Fig. 3i. The gain of the two antennas reaches the maximum at the resonant frequency of 2.45 GHz, which is consistent with the measured |S 21 | (as in Fig. 3i, blue line). The measured results show that the GAF 5G WCE communication system can function reliably, and that the exible 5G GAF antennas and transmission line are capable to t and work on the human body to transmit signals.

Wearable Communication System and 5G Millimeter Wave Antenna with GAF
Millimeter wave WCE, with the advantages of high directivity, small in size, high resolution, rich spectrum resources, and high information security, is an essential technology for the 5G mobile communication 48 .
To investigate GAF's abilities in millimeter wave 5G WCE, GAF-based 5G ultra-wideband (UWB) antenna and 5G antenna array are studied. Fig. 3j-k illustrate the geometry and present a digital photograph of the proposed 5G UWB antenna. The measured -10 dB bandwidth covers the frequency range of 1.6 GHz to 40 GHz with the bandwidth ratio of 25:1, Fig. 3l. Although the test frequency is up to 40 GHz, the actual impedance bandwidth of the 5G UWB antenna is much wider. To gain insight into the radiation characteristics, we simulated the surface current distribution of the UWB antenna at 6 GHz, 10 GHz, 20 GHz, and 40 GHz. As shown in Supplementary Fig. 26, current distribution demonstrates that the UWB antenna is working in its fundamental resonance mode at low frequency band and in higher resonance mode at high frequency band. A GAF 5G millimeter wave antenna array with the geometrical dimensions of 135 mm × 95 mm × 0.54 mm is fabricated, shown in  Fig. 3r, which also con rms the excellent sidelobe performance.

GAF for EMI Shielding
The EMI shielding performance of GAF in the frequency range of microwave band, millimeter wave band and teraherz (THz) band is explored. Firstly, the EMI shiedling effectiveness (SE) at the frequency range of 2.6 GHz -40 GHz is simulated and tested by the rectangular waveguide method, Supplementary  Fig. 29-30. Fig. 4a-c show the EMI SE of the GAF and commerical copper foils. The thickness of EMI SE produced from commercial copper foils (we tested thicknesses of 10 μm and 50 μm) has little effect on their EMI performance and presents an EMI SE of around 100 dB in the 2.6 GHz -40 GHz frequency band. This is due to the fact that copper fully re ects electromagnetic waves and the absorption effect is negligible. Due to the high conductivity, GAF exhibits ultra-high EMI SE. Addtionlly, because of its natural laminate structure, which causes absorption and multiple internal re ections 9 , increasing the thickness of GAF can improve the EMI SE. The proposed GAF's EMI shielding mechanism is in Supplementary Fig. 31. GAF's EMI SE with a thickness of 15 μm is greater than 80 dB and can achieve 90-100 dB above 6 GHz. When the thickness increase to 50 μm, the EMI SE of GAF rises to around 110 -120 dB, especially at 13.5 GHz, where it reaches up to 127.3 dB. When the frequency exceeds 26 GHz, the GAF with a thickness of 15 μm exhibits the same EMI SE as copper foil with a thickness of 50 μm. Furthermore, We use the free space method (Supplementary Fig. 32) to evaluate GAF's EMI shielding performance over the frequency ranges of 40 GHz-67 GHz, 75 GHz-110 GHz, and 0.22 THz-0.325 THz. As shown in Fig. 4d-f, GAF outperforms copper foil in terms of EMI shielding as frequency increases. The EMI SE of the GAF with a thickness of 15 μm and 50 μm is around 60 -80 dB and 80 -100 dB, respectively, which is higher than the 40 -60 dB of copper foil. We compared the recently reported EMI shielding performance of graphenebased and other materials, as shown in Fig. 4g. GAF is the electromagnetic shielding material that is closest to the ideal area, with the highest SE in the same thickness and the thinnest thickness in the same SE. Due to the importance of thickness to EMI shielding materials, SMI SE per unit thickness (SE/t) is used to characterize the EMI performance. Among other graphene structures, carbon nanotubes, carbon bres, and MXene, GAF has the highest SE/t (6966 dB/mm), as shown and compared in Fig. 4h and Supplementary Table 3.

GAF Applied in FSS at Sub-6 GHz and Millimeter Wave Frequencies
In addition to complete electromagnetic shielding, selective shielding of the electromagnetic eld is also important in many cases to ensure the normal transmission of other frequency bands. As a member of metamaterials, frequency selective surface (FSS) is formed by periodic arrangement of structural units, which can selectively absorb, re ect and transmit electromagnetic waves 49 , and thus is an effective way to realize frequency selection. To further explore the electromagnetic protection performance of GAF, we developed two transparent, exible FSS that work in Sub-6 GHz and millimeter wave bands, respectively. Firstly, a miniaturized exible FSS based on GAF that works at 3.5 GHz is designed, Supplementary Fig.  33. The GAF FSS is with 12×12 periodic elements, fabricating by a high precision laser engraving. The structure dimensions are 192 mm×192 mm×0.075 mm, as shown in Fig. 5a, with the optimised parameter values shown in Supplementary Fig. 34 and Table 4. GAF FSS is translucent and has a very low areal density of 0.0087 g/cm 2 . GAF FSS is very exible and can conform to curved surfaces. Because of the presence of the bending line, the edge of the periodic element structure has a strong parasitic capacitance, as shown in Supplementary Fig. 35, which can miniaturise the FSS. A high parasitic capacitance can also assisst FSS maintain its angular stability. The equivalent circuit diagram of the GAF FSS element is shown in Supplementary Fig. 36. The transmission coe cient results of the periodic element are shown in Supplementary Fig. 37. The FSS has a resonance frequency of 3.5 GHz, agreeing with the simulation results. In Fig. 5b, the E-eld distribution can be used to investigate the working mechanism of FSS. It is clear that the FSS resonates at 3.5 GHz and generates a large induced current, preventing electromagnetic waves from passing through the FSS. The measured transmission coe cient and shielding e ciency of GAF FSS under normal incidence of electromagnetic wave is shown in Supplementary Fig. 38-39. Supplementary Fig. 40 is the measuring environment. In the 3.38 -3.91 GHz frequency band, the transmission coe cient of GAF FSS is less than -10 dB, which means that FSS can shield more than 90% of electromagnetic waves. In particular, GAF FSS can shield 99.4% of electromagnetic waves at 3.5 GHz. Outside of this frequency band, electromagnetic waves can pass GAF FSS in a large proportion, proving that GAF FSS has good frequency selection characteristics. Fig. 5c are the spectrum curve of GAF FSS at different incident angles of electromagnetic waves, the transmission coe cient and working bandwidth of GAF FSS remain essentially constant in the 0-25° range, indicating that GAF FSS has high angular stability.
We also designed a low pro le and ultra-wideband exible millimeter wave FSS with a thickness of 0.138λ. The element structure of millimeter wave FSS is illustrated in Supplementary Fig. 41. The digital photos shown in Fig. 5d and Supplementary Fig. 42 demostrate the FSS's exibility. The FSS has the physical dimensions of 125 mm × 125 mm × 0.065 mm implanting with 1600 elements. Supplementary  Fig. 43 illustrates the simulated transmission coe cient. GAF millimeter wave FSS covers a wide -10 dB bandwidth of 8.16 GHz between 55.76 GHz and 63.92 GHz. Supplementary Fig. 44 is the surface current distribution of the GAF millimeter wave FSS at 60 GHz. It can be seen that the FSS resonates at 60 GHz and generates a strong induced current, hindering the passage of electromagnetic waves at 60 GHz. Supplementary Fig. 45 shows the measured transmission coe cient and shielding e ciency of GAF millimeter wave FSS under normal incidence of electromagnetic wave. The GAF FSS can shield 99.9% of electromagnetic waves at 60 GHz. Different bending states of GAF FSS and incident angles of electromagnetic waves can be achieved by varying the distance between two brackets and rotating the disc. As shown in Fig. 5e, the frequency selection performance of GAF FSS remains stable within a bending angle changing between 0° to 40°. Fig. 5f illustrates that GAF FSS maintains good frequency selection performance in the range of electromagnetic waves ± 30° incident angle.

Discussion
Here, we demonstrate a lightweight, exible, mechanically ultra-durable, highly chemically stable, and ultrahigh conductive GAF that can be applied in 5G multi-band wireless communication electronics and electromagnetic protection to overcome the major issues in metal-based electronics. These GAF-based 5G electronics can be designed into a variety of sophisticated patterns and integrated communication systems to achieve a wide range of advanced functions across the entire microwave communication frequency band. GAF has also demonstrated excellent electromagnetic shielding performance in the microwave and terahertz frequency bands, and it can be designed and fabricated into metamaterials to achieve selective electromagnetic wave shielding. Our research demonstrates that the highly conductive graphene lm can be used as an alternative fully functional and sustainable material in radio frequency elds, which can support current and next-generation exible electronics, WCE, and EMI shielding applications.
Methods GAF fabrication. Two major approaches have been utilized to achieve high electrical conductivity of graphene-based laminates. Firstly, we maximized the size of graphene crystallites, which allowed us to reduce the contribution of contact resistance. Secondly, we introduced secondary annealing process and special assembly technique which allows highly laminated, defect free assembly of such graphene crystallites into continuous lms. Firstly, graphene oxide (GO) was prepared via the modi ed Hummers method. The extremely large ake size graphene oxide (LGO) was separated and collected, and use as the lm fabrication precursors. The LGO was separated from graphene oxide suspension (3 wt. %) after seven times repeating centrifugation (the bottom 30% GO are collected each time). An LGO lateral size statistical study is carried out by optical microscope: LGO with the lateral size > 75 µm accounts for 74%, and 54 % of the LGO are > 100 µm. The typical ake size graphene oxide (TGO) was used as it was synthesised and applied as a control experiment. LGO assembled lm was prepared through pre-metered roll transfer coating of LGO hydrogel on a self-released substrate such as polyethylene terephthalate (PET) lms. Subsequently, the LGO hydrogel on substrate was heated (70-80℃) for drying. Thereafter, a soft, dark brown free-standing and paper-like graphene oxide lm (LGO lm) could be easily peeled off from the PET substrate. In this step, the anisotropic liquid crystalline behaviour of LGO hydrogel can lead to a pre-aligned orientation structure after force directed rolling transfer. This highly ordered laminate can be converted into a pristine graphene lm in meters long scale via a high temperature graphitization process.
LGO lm was thermally annealed at 1300℃ for 2 hours and 2850℃ for 1 hour in Ar atmosphere between two graphite plates for reduction and graphitic crystallisation. The giant crystalline graphitic domain size in graphene assembled lm (GAF) is formed by the coalescence of neighbouring reduced LGO sheets 50 . Graphene lms are fully graphitized after primary high temperature annealing, allowing dangling-bond-free graphene nanosheets to tile on each other with broad-area plane-to-plane contacts. A rolling compression with the pressure of 300 MPa was further introduced to obtain the nal GAF. The following rolling compression contributes to eliminate inter layer gaps and contact resistance, also leads to an excellent exibility. Followed by the rolling compression, a secondary high temperature annealing process at 2850℃ in Ar atmosphere was carried out to further remove the structural damage during the rolling process to increase the electrical conductivity 51 . TGF was obtained with same method but from the TGO. GAF WCE fabrication. Laser engraving (with high resolution up to micrometre scale) was proposed and investigated to manufacture sophisticate GAF patterns (Supplementary Fig. 45). First, the GAF and the dielectric substrate (FR-4, Silica gel lm, Rogers 5880, PET) were combined by hot pressing to form GAF Printed Circuit Board (PCB) 29 . To adapt the laser engraving machine, the carving patch of the device dimensions output by the simulation software was calculated using LPKF CircuitPro PL 2.0. The GAF devices were manufactured in one step by a laser engraving machine (LPKF Laser & Electronics ProtoLaser S) using the calculated laser path.
Dipole antenna design and measurement. The dipole antenna was designed on the FR-4 substrate having a thickness (h) of 1.6 mm and dielectric constant of 4.4. Both the width (W) of the arm and the gap (g) between the two arms were 3.53 mm, and the arm length (L) was 63.95 mm. For the convenience of testing, two arms of the dipole antenna were connected by a SMA connector via conductive adhesive. To verify the performance of the GAF antenna, antennas made by graphite, HOPG, TGF and copper with same design were carried out for comparation. The re ection coe cient was measured in a microwave anechoic chamber with a Network Analyzer (PNA, Keysight N5247A). The gain was calculated by placing two identical antennas in microwave anechoic chamber and measuring the forward transmission coe cient (|S 21 |) according to the following formula Where P L is path loss in dB, λ is the wavelength at the resonant frequency, G (dB) is the antenna gain with respect to an isotropic source, r=2.8 m is the distance between two antennas. The measurement frame diagram is shown in Supplementary Fig. 46. The radiation patterns were tested using the antenna measurement system (Diamond Engineering Automated Measurement Systems). The GAF antenna was placed on the rotating platform as a receiver, and the standard reference antenna (REF antenna) was xed at the same level as a radiator. The data was recorded for every 10° of rotation. All measurements were performed in a microwave anechoic chamber. Wearable antenna design and measurement. The substrate of the microstrip antenna was silica gel lm with a thickness of 1.5 mm. The length and width of patch were 31.37 mm and 40.37 mm, respectively. In order to achieve miniaturization, the GAF antenna adopted a 50Ω microstrip embedded feeding structure, and the width of the feeding microstrip line was 3.32 mm. The patch and ground were made of exible GAF.
Design and measurement of 2×2 antenna array. The 2×2 antenna array was designed on the FR-4 substrate. The length and width of element patch were 28.53 mm and 37.26 mm, respectively. In order to reduce mutual coupling and grating lobe, the distance between the two elements was 0.7 λ, and the parallel feed network was used. T-type power divider and quarter wavelength impedance converter were Measurement of EMI SE. A series of rectangular waveguides are used to measure the electromagnetic interference shielding performance of GAF in WR-284, WR-187, WR-137, WR-90, WR-62, WR-42, WR-28 bands. The GAF is carved to a speci c dimension as test sample to t the rectangular waveguide. A foam with the same length and width and a thickness of 2 mm is used to support the GAF test sample. The vector network analyzer (Keysight PNA N5247A) is used to record the transmission coe cient and re ection coe cient of the rectangular waveguide test sample. According to the S-parameter, the EMI SE, re ectance and transmittance of the test sample can be calculated. Before the test, we qualitatively studied the EMI shielding performance of GAF through simulation. In the 40 GHz-0.32 THz frequency band, the free space method is used to test the EMI SE of GAF. The two ports of the vector network analyzer (Keysight PNA N5247A, N5256AW10, N5256AW03) are connected to the horn antenna to measure the EMI SE of GAF.
Design and measurement exible frequency selective surface. The GAF with a typical thickness of 15 µm is selected as the conductor of Sub-6 GHz and millimeter wave FSS. PET lm with a thickness of 0.06mm, dielectric constant of 3.5 and loss tangent of 0.003 is the substrate of GAF FSS. The performances of GAF FSS were measured in the microwave anechoic chamber to avoid the in uence of external electromagnetic wave. The two horn antennas were placed in opposite directions. The vector network analyzer (Keysight PNA N5247A) records the re ection coe cient and transmission coe cient of the two antennas to calculate the frequency response of the GAF FSS. Firstly, the transmission coe cient of the two horn antennas without FSS was measured. The GAF FSS was then placed between the two horn antennas, and the transmission coe cient was measured again. Subtracting two results was the corresponding transmission coe cient for GAF FSS. In order to reduce the electromagnetic wave re ection of the bracket, a certain area of absorbing material was wrapped around the horn antenna. The GAF Sub-6 GHz FSS and millimeter wave FSS were placed on a rotatable disc and xed by two horizontally movable brackets and a rotatable wooden shelf respectively in order to test the performance  graphene ink (G-ink), carbon nanotubes (CNT) and MXene; (g) Resistance change of GAF with 100,000 repeating bending test to proof durable exibility and stability; (h) Flexible GAF FCPW TL being bent with diameters of 60mm, 40mm, 20mm and twisted 180°; (i) Transmission coe cient of the FCPW TL in different states between 10 MHz to 40 GHz frequency band (red-at, orange-60 mm, wathet-40 mm, blue-20 mm, and purple-twisted); (j) Flexible GAF λ/4 short-circuited resonator at di dent twisting condition: un-twisted, twisted 90°, 180°, 360° and 540°; (k) Resonator's re ection coe cient results at different twisting condition, between 10 MHz to 12 GHz frequency band (red-at, orange-90°, wathet-180°, blue-360°, and purple-540°). references with the results in this work; (i, j) Digital photo of GAF and copper dipole antennas after one week and two weeks salt spray; (k) Measured and simulated |S11| of GAF antenna, initial, after one week and two weeks salt spray; (l) Measured |S11| of copper antenna, initial, after one week and two weeks salt spray; (m) The measured gain of GAF and copper antennas at 865 MHz with initial, after one week and two weeks salt spray.

Supplementary Files
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