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.