Conclusion

This study investigated the impact of skin pigmentation on photoplethysmography using an advanced perfused vascular finger phantom combined with Monte Carlo modelling. The 3D-printed PVA sacrificial template approach enabled the fabrication of a geometrically complex, distributed vascular network that represented a fundamental advance over simplified single-vessel phantom designs, allowing PPG signal acquisition across all wavelengths and skin tones. Increasing pigmentation produced consistent reductions in PPG amplitude, SNR, and AC/DC ratio across wavelengths, consistent with increased absorption in the skin layers. These effects were most pronounced at shorter wavelengths and in reflectance mode, where superficial absorption dominates photon transport, while longer wavelengths preserved deeper vascular sensitivity. Monte Carlo simulations provided mechanistic insights by linking these trends to superficial photon energy deposition, effective penetration depth, and reduced interaction with pulsatile blood volumes. Consistent directional agreement between simulated optical metrics and experimental PPG features supports the validity of the combined experimental-computational framework. Overall, this combined approach supports improved understanding and evaluation of light–tissue interaction under varying skin pigmentation conditions, with direct relevance to emerging wearable devices and PPG-based applications that extend beyond pulse oximetry, including blood pressure estimation, arterial stiffness assessment, and other cardiovascular markers, where reduced signal quality due to skin pigmentation may directly impact algorithm performance.