Additive manufacturing of complex structures with spatially varying electromagnetic properties can enable new applications in high-technology sectors such as communications and sensors. This work presents the fabrication method as well as microstructural and dielectric characterization of bespoke composite filaments for fused deposition modeling (FDM) 3D printing of microwave devices with a high relative dielectric permittivity $ϵ=11$ in the GHz frequency range. The filament is composed of 32 vol % of ferroelectric barium titanate (BaTiO ${}_3$ ) micro-particles in a polymeric acrylonitrile butadiene styrene (ABS) matrix. An ionic organic ester surfactant was added during formulation to enhance the compatibility between the polymer and the BaTiO ${}_3$ . To promote reproducible and robust printability of the fabricated filament, and to promote plasticity, dibutyl phthalate was additionally used. The combined effect of 1 wt % surfactant and 5 wt % plasticizer resulted in a uniform, many hundreds of meters, continuous filament of commercial quality capable of many hours of uninterrupted 3D printing. We demonstrate the feasibility of using the high dielectric constant filament for 3D printing through the fabrication of a range of optical devices. The approach herein may be used as a guide for the successful fabrication of many types of composite filament with varying functions for a broad range of applications.

Computer-aided design software and additive manufacturing provide flexibility for the direct fabrication of multi-material devices. This design and fabrication versatility has been investigated for the manufacture of dielectric spiral phase plates (SPP) that generate electromagnetic waves with helical wavefronts. Three types of SPPs designed to produce an orbital angular momentum (OAM) mode number l = |1| were additively manufactured using material extrusion and polyjet fabrication methods. The OAM mode characteristics of the transformed helical microwaves as a function of the SPP geometrical features were investigated experimentally in the 12–18 GHz frequency range. The SPPs were further combined with an additively manufactured dielectric lens that provided a marked improvement in OAM mode purity. Finally, multiplexing and de-multiplexing of two OAM modes were demonstrated successfully using an optimum SPP geometry and arrangement.

Extreme high-speed laser material deposition (EHLA) is a laser-based coating process known for its high deposition rates and excellent resource efficiency. To further increase productivity, higher laser powers and powder feed rates are increasingly used, but this also raises the thermal load on the processing head due to back-reflected radiation. Inclining the processing head or substrate helps deflect this radiation, while also enabling coatings in geometrically constrained areas, such as internal surfaces. However, inclination introduces asymmetries in the powder and laser distribution, potentially affecting track formation and melt pool behavior. This study investigates how inclination between the processing head and a rotationally symmetric substrate influences track geometry, surface quality, dilution, and thermal impact. Two inclination configurations were examined across a range of angles, with systematic variation of feed and rotation direction to simulate pushing and pulling deposition strategies. The results reveal that inclination has a significant and configuration-dependent effect on surface roughness, build-up volume, powder catchment efficiency, and thermal penetration. Variations in asymmetry orientation relative to the motion direction lead to measurable differences in coating properties. The findings offer new insights into optimizing EHLA process parameters for inclined setups, contributing to more robust and application-specific coating strategies.