A multilayered skin-fat-muscle phantom embedded with thermocouples for non-ablative RF heating: numerical simulation and experimental validation

BACKGROUND: Non-ablative radiofrequency (RF) skin rejuvenation relies on controlled volumetric heating of skin and subcutaneous tissues. Clinical validation is costly and ethically constrained, while simulations require experimental validation. Existing single-layer phantoms cannot capture electrothermal heterogeneities across tissue layers. PURPOSE: To develop a thermocouple-embedded, skin-fat-muscle-mimicking multilayered phantom (MLP) that simulates electrothermal behavior relevant to RF skin rejuvenation and enables depth-resolved temperature measurement for benchtop evaluation and model validation. METHODS: A three-layer MLP (skin, fat, and muscle) was fabricated. Electrical conductivity and thermal properties (thermal conductivity, density, specific heat) were measured and compared with literature-reported human tissue ranges. Three thermocouples were embedded at depths of -1, -3, and -4 mm to record transient temperature under multiple RF voltage settings. A 3D coupled electrothermal simulation was built to replicate the experimental setup, and the simulated results were quantitatively compared with the measured results using temperature difference and temperature rise as primary metrics. A single-layer skin phantom (SLSP) was evaluated in parallel for comparison. RESULTS: MLP properties fell within reported ranges. Simulated temperature profiles showed strong agreement with experiments for both SLSP and MLP (most temperature differences <4%, and most deviation of temperature rise <0.5 °C). Compared with SLSP, MLP simulated temperature rise more closely matches layer-dependent temperature evolution across depth. CONCLUSIONS: The MLP with embedded thermocouples provides a reproducible platform for depth-resolved temperature characterization of RF-induced heating and for experimental validation of simulations, supporting efficient screening and benchmarking of RF device settings and electrode designs.