Frequency-domain multiphysics modeling of photoacoustic responses in strongly scattering multilayered human skin

This work presents a frequency-domain semi-analytical framework for modeling photoacoustic wave generation and propagation in strongly scattering multilayered human skin. The approach extends previous semi-analytical methods for non-scattering multilayered media by incorporating photon diffusion and its coupling with heat conduction and thermoelastic wave generation within a unified Fourier-domain formulation, enabling accurate characterization of frequency-dependent acoustic responses. A key contribution is the physically consistent treatment of photon transport at refractive-index discontinuities, resolving inconsistencies that can arise when Robin-type conditions are applied at internal interfaces in some diffusion-based layered models. This ensures photon-flux continuity and optical energy conservation across anatomical interfaces, which is critical for accurate predictions in scattering-dominant media. The formulation is validated against benchmark reference results, demonstrating excellent agreement in pressure amplitude and phase. Application to a realistic nine-layer anatomical skin model enables depth-resolved analysis of photon fluence, thermal behavior, and acoustic pressure under physiologically relevant conditions. The proposed framework provides an energy-conserving and generalizable foundation for quantitative photoacoustic analysis in layered biological media, offering improved physical fidelity for biomedical ultrasound and photoacoustic imaging applications.