In-line measurement of the dielectric permittivity of materials during additive manufacturing and 3D data reconstruction

Abstract

Additive manufacturing (AM) techniques are used increasingly for the direct fabrication of microwave devices, such as graded index lenses and dielectric resonator antennas, which have spatially-varying dielectric properties (i.e. relative permittivity) that are difficult to manufacture using traditional methods. However, there is no effective method to characterize the spatial distribution of permittivity within the printed component, either during manufacture or once the component is complete. Therefore it is not possible to confirm the extent to which the manufactured spatial distribution of permittivity meets the intended design. We report the integration of a novel split ring resonator (SRR) surface mapping technique directly into an AM process to make non-destructive in-line measurements of the local relative dielectric permittivity (ϵr) within 3D objects as they are formed. We then reconstruct these data into 3D dielectric “images” of the printed component. Detailed insights into the dielectric imaging principle, data processing/analysis, as well as limitations and opportunities related to the technique are described. The work aims to accelerate the design-make-test cycle for advanced microwave devices, and suggests the possibility for real-time, closed-loop control of dielectric properties during AM.