A stacked cavity-backed metamaterial antenna for confined hyperthermia of subcutaneous fat in ISM band.

Introduction: Hyperthermia has emerged as a versatile modality in oncology, rehabilitation, and aesthetic medicine, yet conventional RF devices often suffer from insufficient penetration and collateral epidermal heating. This study proposes a miniaturized stacked cavity-backed antenna operating in the 2.4-2.5 GHz ISM band for depth-confined heating of facial subcutaneous fat. Methods: By leveraging the strong dielectric contrast at the skin-fat boundary, the design enhances the normal electric-field component in adipose tissue to promote preferential power deposition without active epidermal cooling. Electromagnetic simulations quantify field and SAR confinement, and multiphysics thermal simulations evaluate short-pulse therapeutic operation. The methodology is validated through ex vivo porcine experiments and a preliminary in vivo human feasibility test (10 W, surface thermography). Results: The results confirm reproducible superficial warming at the target depth without adverse skin reactions. The study successfully demonstrates single-element hardware feasibility and effective depth-selective energy confinement within the subcutaneous fat layer. Conclusion: This research establishes the fundamental hardware capability for targeted facial hyperthermia. However, macroscopic treatment-uniformity protocols and long-term clinical efficacy remain topics for future clinical studies.