This paper discusses the design and fabrication of a low-profile Hilbert-shaped metamaterial (MTM) array-based antenna, forming a rectangular patch with partial ground plane backing; the rest is slotted with traces for RF energy harvesting. The antenna is mounted on a 28 mm × 32 mm indium nickel oxide polymerized palm fiber (INP) substrate and compared to the identical one based on FR4 substrate. The two prototypes are printed with silver nanoparticles. Numerical and experimental tests are applied to the antenna performance in terms of S11 and radiation patterns. The obtained antenna gain bandwidth product of the INP prototype is found to be significantly better than the FR4 prototype. The proposed INP antenna gain at 5.8 and 8 GHz frequencies is found to be about 4.56 and 7.38 dBi, respectively, while the FR4 antenna gain is found to be 4.56 and 6.85 dBi at 5.8 and 8 GHz, respectively. Finally, the resultant DC voltage and the efficiency of conversion from harvested RF energy are measured experimentally at 5.8 and 8 GHz for both proposed prototypes.