Multifunctional graded dielectrics fabricated using dry powder printing

Abstract

The ability to fabricate multifunctional devices that combine good structural properties with embedded electromagnetic functionality has many practical applications, including antireflective surfaces for structural radomes, load bearing conformal antennas, integrated RF transmission lines and passive beam forming networks. We describe here a custom made 3D printer that can print high dielectric constant ceramic powders within a low-loss structural composite substrate to produce mechanically robust parts with integrated graded dielectric properties. We fabricated a number of these parts and evaluated their anisotropic dielectric properties by determining the complete permittivity tensor of the printed samples as a function of local powder weight. This data was then experimentally validated using two practical examples: a Chebyshev antireflective stack and a 2D passive beamsteering network. The results of both electromagnetic systems displayed acceptable agreement between the simulated and measured results. This agreement shows that powder printing is a potential approach for fabricating spatially graded dielectric electromagnetic systems.

Electromagnetic and Electronic Aerospace Conformal Load-Bearing Smart Skins: A Review

“…Another example using 3D printing technology in conformal load-bearing antenna structures (CLAS) applications was presented in [174]. The custom designed powder dispensing head was used to deposit a high permittivity powder onto a low-loss woven fabric based composite pre-preg material [174]. They used this method to manufacture the 3D composite structure by stacking together multiple layers with powder deposited on them.…”

A Review on Functionally Graded Materials and Structures via Additive Manufacturing: From Multi‐Scale Design to Versatile Functional Properties

“…[ 211 ] Through the 2D phase response near the surface of the lens at an incident frequency of 15 GHz, the measurement in the x ‐direction and x‐y plane (Figure 17c,d) showed graded dielectrics, indicating that graded index lenses had been successfully produced. [ 210,212,215 ]…”

“…Spatially varied refractive index gradients have been applied in anti-reflective surfaces, passive beamformers and graded index lenses. [210][211][212][213] Conventional technologies, including ion exchange and sol-gel techniques, with common limitations such as long processing times (typically >100 h) and limited component sizes (typically <13 mm), can be overcome by using FGMs and FGSs. [214] Roper et al [210] printed dielectric powders (ECCOSTOCK HiK) on fabric-glass composite substrates (S-glass/cyanate ester fiber reinforced via ultrasonic powder deposition.…”

“…[211] Through the 2D phase response near the surface of the lens at an incident frequency of 15 GHz, the measurement in the x-direction and x-y plane (Figure 17c,d) showed graded dielectrics, indicating that graded index lenses had been successfully produced. [210,212,215] Figure 16. a) Photographs of fabricated GRINRAS: local and top view of a ring and board-shaped GRINRAS with a woodpile unit cell.…”