Conductivity measurement using 3D printed re-entrant cavity resonator

A technique for measuring effective conductivity of conductor materials using 3D printed re-entrant cavity resonator is proposed. An analytical formula for the extraction of the effective conductivity has been derived in relation to energy stored in the volume of the cavity geometry. A method of resonant cavity characterisation of material based on microwave losses is utilised for the measurements. The approach offers a simplified analytical method and also supports the measurements of sample with arbitrary thickness. Samples produced from three different manufacturing processes of computer numerical control (CNC) and 3D printing, made of aluminium, copper and stainless steel were measured to demonstrate the method. The 3D printed and copper coated polymer sample is considered as reference material for the measurements. The measured results have shown that the copper coated polymer sample have similar conductivity with that CNC copper. This signifies the good finishing, low surface roughness and quality of copper coating used in 3D printed polymer device.