3D Printed Coaxial Transmission Line Using Low Loss Dielectric and Liquid Metal Conductor

This paper introduces an innovative method to fabricate a coaxial transmission line using a low-loss 3D printed dielectric and a liquid metal conductor. The dielectric part is 3D printed from a low loss factor resin, cyanate ester (tanδ = 0.0046). The inner conductor is formed by pumping eutectic gallium indium (EGaIn) through the empty channel of the dielectric part, and the outer conductor is electrolessly plated with silver and then coated with EGaIn. An implemented 2-inch straight coaxial line shows a measured insertion loss of 0.26 dB/cm at 10 GHz, which is 1/3 of that of a coaxial line using a common 3D printing material, Visi.let Crystal M3. In addition, a 2-ns 3D printed coaxial delay line was fabricated and it achieved a low dispersion at the measured group delay of 2ns ± 88ps, as 4.4% variation from 0 to 10 GHz.