Laser-induced graphene-based frequency selective surface embedded in MWCNT/PDMS composites

In this study, a radar-absorbing material (RAM) was developed by transferring a laser-induced graphene (LIG)-based frequency selective surface (FSS), formed on a polyimide (PI) film, onto a multiwalled carbon nanotube (MWCNT)–polydimethylsiloxane (PDMS) composite. Unlike prior works that retained the PI substrate within the absorber structure, this study introduces a novel transfer process where the LIG pattern is embedded into the PDMS matrix, allowing the PI film to be completely removed. This approach avoids potential interfacial adhesion issues between materials and is expected to improve structural compatibility. To validate the proposed method, the sheet resistance of LIG was analyzed under varying laser parameters, showing a minimum of 31.75 Ω/sq (0°) and 44.95 Ω/sq (90°) at 9% power and 200 mm/s speed. After transfer, resistance increased to 37.56 Ω/sq (0°) and 69.67 Ω/sq (90°) due to PDMS infiltration. A square loop FSS was designed with key geometric and dielectric variables to achieve broadband performance. Despite the anisotropy in sheet resistance induced by the laser scanning direction, the fabricated LIG-FSS RAM with a thickness of 3.2 mm and a dielectric constant of 4.91 – j0.81 (at 10.3 GHz) achieved more than 90% absorption across the full X-band (8.2–12.4 GHz), corresponding to an absorption bandwidth of 4.2 GHz. Furthermore, a minimum reflection loss of –18.07 dB was observed at 10.4 GHz, demonstrating the strong potential of LIG-based FSS structures as high-performance electromagnetic absorbers.