| Summary: | The formulation of a high dielectric permittivity ceramic/polymer composite feedstock for daylight vat photopolymerization 3D printing (3DP) is demonstrated, targeting 3DP of devices for microwave and THz applications. The precursor is composed of a commercial visible light photo-reactive polymer (VIS-curable photopolymer) and dispersed titanium dioxide (TiO<sub>2</sub>, TO) ceramic nano-powder or calcium copper titanate (CCT) micro-powder. To provide consistent 3DP processing from the formulated feedstocks, the carefully chosen dispersant performed the double function of adjusting the overall viscosity of the photopolymer and provided good matrix-to-filler bonding. Depending on the ceramic powder content, the optimal viscosities for reproducible 3DP with resolution better than 100 µm were η<sub>(TO)</sub> = 1.20 ± 0.02 Pa.s and η<sub>(CCT)</sub> = 0.72 ± 0.05 Pa.s for 20% <i>w</i>/<i>v</i> TO/resin and 20% <i>w</i>/<i>v</i> CCT/resin composites at 0.1 s<sup>−1</sup> respectively, thus showing a significant dependence of the “printability” on the dispersed particle sizes. The complex dielectric properties of the as-3D printed samples from pure commercial photopolymer and the bespoke ceramic/photopolymer mixes are investigated at 2.5 GHz, 5 GHz, and in the 12−18 GHz frequency range. The results show that the addition of 20% <i>w</i>/<i>v</i> of TO and CCT ceramic powder to the initial photopolymer increased the real part of the permittivity of the 3DP composites from ε’ = 2.7 ± 0.02 to ε’<sub>(TO)</sub> = 3.88 ± 0.02 and ε’<sub>(CCT)</sub> = 3.5 ± 0.02 respectively. The present work can be used as a guideline for high-resolution 3DP of structures possessing high-ε.
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