Harvesting of ambient radio-frequency energy is largely covered in the literature. The RF energy harvester is considered most of the time as a standalone board. There is an interest to add the RF harvesting function on an already-designed object. Polymer objects are considered here, manufactured through an additive process and the paper focuses on the rapid prototyping of the harvester using a plastronic approach. An array of four antennas is considered for circular polarization with high self-isolation. The RF circuit is obtained using an electroless copper metallization of the surface of a 3D substrate fabricated using stereolithography printing. The RF properties of the polymer resin are not optimal; thus, the interest of this work is to investigate the potential capabilities of such an implementation, particularly in terms of freedom of 3D design and ease of fabrication. The electromagnetic properties of the substrate are characterized over a band of 0.5–2.5 GHz applying the two-transmission-line method. A circular polarization antenna is experimented as a rapid prototyping vehicle and yields a gain of 1.26 dB. A lab-scale prototype of the rectifier and power management unit are experimented with discrete components. The cold start-up circuit accepts a minimum voltage of 180 mV. The main DC/DC converter operates under 1.4 V but is able to compensate losses for an input DC voltage as low as 100 mV (10 $\mathsf{\mu }$W). The rectifier alone is capable of 3.5% efficiency at −30 dBm input RF power. The global system of circularly polarized antenna, rectifier, and voltage conversion features a global experimental efficiency of 14.7% at an input power of −13.5 dBm. The possible application of such results is discussed.