This study presents an effective method to model, analyse and design graphene metasurface-based terahertz (THz) absorbers using equivalent circuit model approach. Broadband and tunable absorbers consisting of graphene metasurface and metal-backed dielectric layer have been designed based on the formulas derived from this approach and verified by full-wave electromagnetic simulation. By properly constructing the graphene metasurface, broadband absorption over 70% fraction bandwidth has been achieved, showing that graphene can provide a wideband absorption in the low THz spectrum. Furthermore, tunability of the graphene metasurface has also been investigated. It is demonstrated that the absorption peak frequencies can be tuned while maintaining the peak absorption unchanged, which is highly desirable for THz sensing applications.

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The potential of highly flexible and conductive graphene laminate is extended to the application of electromagnetic interference shielding. Graphene nanoflake-based conductive ink is printed on paper, and compressed to form a graphene laminate with a conductivity of 0.43 × 10 5 S/m. The shielding effectiveness is experimentally measured to be above 32 dB between 12 and 18 GHz, even though the thickness of the graphene laminate is only 7.7 µm. It is demonstrated that graphene has great potential in offering lightweight, lowcost, flexible and environmentally-friendly shielding materials.Introduction: Electromagnetic interference (EMI) shielding materials have attracted increasing intensive research attention due to the wide use of electronic and communication facilities in commercial and military areas [1]. The shielding materials are normally required to be conductive to increase the reflection loss. In general, there are mainly three catalogues of conductive materials presented for EMI shielding, which are metals, conductive polymers and carbon nanomaterials. Metals such as silver are heavy and expensive even though they offer high conductivity. Conductive polymers are low cost; however, their conductivity is not high enough [2, 3]. Moreover, as polymer is limited by chemical and thermal stability, it is therefore, not suitable for high-temperature application fields [3,4]. However, carbon nanomaterials, especially graphene, are quite competitive in providing high conductivity along with advantages in cost, chemical/thermal stability and flexibility [5]. Previously, monolayer graphene was studied for EMI shielding, but the shielding effectiveness (SE) is low due to the ultrasmall thickness [6]. Graphene/polymer combinations were also reported, but the SE requires further improvement and some are not environmentally friendly [7,8]. In this Letter, we present a lightweight, highly conductive, flexible and environmentally-friendly graphene nanoflake-based shielding material, and experimentally verify its potential in providing high SE.In this Letter, the EMI shielding material is made of graphene ink (Grat-ink 102E, Bluestone Global Tech) [9]. Fig. 1 shows the procedure for making highly flexible and conductive graphene-based shielding materials. As shown in Fig. 1a, this conductive ink contains graphene nanoflakes, dispersants and solvents, and is printed on normal paper with screen-printing technology. After drying for 10 min at 100°C, dispersants and solvents are volatilised, and graphene nanoflakes are left on the substrate, as shown in Fig. 1b. The good film-forming ability of two-dimensional graphene nanoflakes causes adhesion of the graphene coating. However, the conductivity of the graphene coating is still low (σ = 8.3 × 10 2 S/m). This is because the stacking of graphene nanoflakes is highly porous, and the contact resistance between flakes is high, as illustrated in the scanning electron microscope (SEM) image in Fig. 1b. To increase conductivity, a rolling compression is applied to reduce the contact res...

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