The localized absorption of radio frequency (rf) energy in biological tissue would benefit applications ranging from neuromodulation to cancer hyperthermia. Though previous works have made progress toward this goal, there remains an opportunity to experimentally demonstrate the ability to concentrate and focus rf energy deep within tissues or realistic tissue phantoms while minimizing background absorption in the surrounding medium. In this work, we present both theoretical and experimental demonstrations of “radioplasmonics,” the rf counterpart to optical plasmonics, enabling the manipulation of electromagnetic waves in the rf regime with similar principles. Specifically, we demonstrate that by tuning the dielectric functions and geometries of metamaterials with negative permittivity in the rf spectrum, we can achieve resonant absorption in specific biological tissues. We further provide heatmaps visualizing the resonance in dielectric space as a function of tissue type, applied frequency, and implant geometry. We also present the first known experimental demonstration of radioplasmonic heating in a biological tissue phantom, measuring strong resonant absorption of incident radio waves by rf metamaterials. To the best of our knowledge, this work includes the greatest differential-absorption ratio ever measured for an rf-absorbing material implanted deep within a tissue phantom.

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• Medical devices
• Plasmonics
• Radio frequency techniques
• Wireless power transfer
• Biological materials
• Composite materials
• Metamaterials
• Tissues