Development of a photoplethysmography testing platform using stereolithography 3D printing to create human finger optical phantoms with vascular channels for wearable device applications

Photoplethysmography (PPG) is a widely used, non-invasive optical technique but is affected by various confounding factors in human skin, such as patient pigmentation, sensor geometries, and blood composition. There is a need for adaptable testing platforms to better understand how these confounders impact optical sensors. This study aims to develop a low-cost, reproducible platform for rapid assessment of PPG devices. An anatomical finger model was created using SolidWorks, with U-shaped digital palmar arteries designed and printed in photopolymer resin through stereolithography. Pulsations simulating blood flow were generated using a peristaltic pump and a blood analog solution. Several vessel diameters were tested to simulate human vasculature, with successful reproducibility observed for diameters greater than 2.8mm. Pulsatile signals were captured using multi-wavelength PPG, spanning from blue to infrared light. The system is highly customizable, with interchangeable components that offer flexibility to be adjusted and can ameliorate the burden of testing on patients and animals. Future work will integrate an epidermal layer containing melanin to more accurately model skin interactions. This platform is timely, given the ongoing investigation by regulatory bodies into pulse oximeter testing and its role in equitable device development.