Flexible expanded-graphite based metamaterial absorber for enhanced conformal energy harvesting applications

This article presents an efficient and cost-effective ultrathin, flexible microwave metamaterial absorber for energy harvesting applications. The unit cell of the metamaterial absorber is made up of non-metallic expanded graphite (EG) fabricated on a linear low-density polyethylene (LLDPE) substrate. The absorber with a thickness of 1.5 mm, exhibits an absorption bandwidth of 0.94 GHz with full width at half maxima (FWHM) of 9.9%. Numerical simulations using CST Microwave Studio confirm stable performance under varying polarization angles and bending conditions. Prior to the fabrication, the formation of expanded graphite is validated using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) images analysis. The experimental authentication of the developed metamaterial absorber is done by waveguide technique. Beyond its electromagnetic performance, the use of EG offers distinct advantages over traditional metallic absorbers, including corrosion resistance, bio-compatibility for wearable technology, and simplified large-scale fabrication.