This paper discusses the design of a Radio Frequency (RF) energy harvester working at 2.45 GHz in relation with an emerging fabrication technique, 3D Plastronics. The design consists of an omni-directional circularly polarized system of four antennas with high self-isolation, a multi-port rectifier and a power management circuit (PMC). The RF circuits are obtained using an electroless metallization of the surface of a 3D substrate fabricated using stereolithography, a method of additive manufacturing. The electromagnetic properties of the substrate are characterized over a band of 0.5-2.5 GHz applying the two transmission lines method. The prototype of rectifier and PMC are experimented with discrete components for the verification of operation. The results indicate a global efficiency of 14.7% at an input power of -13.5dBm on each rectifier’s input. The performance of the prototype will be improved using a new version of PMC with a specially designed Integrated Circuit of active components and a Capacitive Interposer (target of 5% of efficiency at -25dBm input power of the PMC).