Integrated CNT–Co Honeycomb Metamaterial Platform for Broadband RF Energy Harvesting and Self-Powered Electronics

The rapid deployment of renewable energy systems is reshaping global power infrastructure, yet life-cycle analyses reveal persistent carbon emissions associated with their manufacture and deployment. In parallel, the proliferation of wireless networks has saturated modern environments with ambient radiofrequency (RF) fields, which are increasingly recognized both as a pollutant and as an untapped energy resource. Here we report a 3D-printed CNT-Co metamaterial antenna that converts far-field RF radiation into usable electrical power with broadband efficiency. By integrating carbon nanotubes and cobalt nanoparticles into a UV-curable resin, we achieved strong conduction and magnetic losses that, when combined with a honeycomb metamaterial architecture, delivered absorption efficiencies up to 99.9% across dual frequency bands (3.35-4.59 GHz and 9.45-16.57 GHz). The system outperformed a commercial Wi-Fi antenna by factors of up to three under low input powers, maintained stable operation in ambient environments, and powered practical devices including LEDs, medical sensors, and wireless trackers. These results establish CNT-Co metamaterial antennas as a scalable platform for harvesting energy from the electromagnetic environment, opening new pathways toward sustainable, battery-free electronics.