In this article, we propose to apply 3-D printing technology to the design and realization of honeycomb microwave absorbers. First, printability of simple honeycomb structures, made of a lossy dielectric material, was evaluated and validated by measurement in the 2–18 GHz frequency band. Effective dielectric properties of honeycomb structures with different dimensions are also discussed. Then, the interest of 3-D printing technology was highlighted by the design, fabrication, and measurement of a multiscale honeycomb absorber that can significantly increase the relative bandwidth. The 3-D printed honeycomb absorbers are compared with others technologies. The potential of this technology was also illustrated by the fabrication and measurement of a pyramidal honeycomb absorber that demonstrates an absorption level of more than 22.9 dB over the 2–18 GHz frequency band.

With the multiplication of electronic devices in our daily life, there is a need for tailored wideband electromagnetic (EM) absorbers that could be conformed on any type of surface-like antennas for interference attenuation or military vehicles for stealth applications. In this study, a wideband flexible flat electromagnetic absorber compatible with additive manufacturing has been studied in the X-Ku frequency bands. A multilayer structure has been optimized using a genetic algorithm (GA), adapting the restrictions of additive manufacturing and exploiting the EM properties of loaded and non-loaded filaments, of which the elaboration is described. After optimization, a bi-material multilayer absorber with a thickness of 4.1 mm has been designed to provide a reflectivity below −12 dB between 8 and 18 GHz. Finally, the designed multilayer structure was 3D-printed and measured in an anechoic chamber, achieving −11.8 dB between 7 and 18 GHz. Thus, the development of dedicated materials has demonstrated the strong potential of additive technologies for the manufacturing of thin wideband flexible EM absorbers.

In this paper, we present narrow-band substrate integrated waveguide (SIW) millimeter wave band-pass filters, designed using cyclo-olefin polymers (COP). The structures were molded, drilled, and metalized with a laser direct structuring (LDS) process. COP are a type of thermoplastic with low dielectric losses in the millimeter waveband, typically 7.5 × 10⁻⁴ at 40 GHz for the COP RS420-LDS from Zeon^®. The body of the filter was realized using a molding process that facilitates the combination of thin 50 Ω microstrip access lines with high thickness microwave cavities through 3D transitions, thus making high quality factors attainable. The simulations and experimental results are presented and discussed.

Three-dimensional printing of microwave absorbers gave rise to new shape optimization possibilities. However, new printable materials dedicated to this application have to be developed. In this study, an iron flake polymer composite was elaborated and characterized. Scanning Electron Microscopy observations demonstrated that iron flake particles are naturally aligned along the flow direction in the nozzle without applying a magnetic field during the 3-D printing process. Magnetic anisotropy was demonstrated with both vibrating sample magnetometer and microwave measurements. Indeed, at 5.4 GHz, a ratio of 1.67 between parallel and perpendicular susceptibility was observed. These measurements demonstrated a self-induced magnetic anisotropy that can be used to control the angular robustness of free-space microwave absorbers. Simulations show that an induced planar anisotropy allows for improving better stability of absorption at oblique incidence compared to an isotropic absorber.