Influence of external contact pressure in reflection mode photoplethysmography
a multidimensional manufacturing approach
Rithvik Bangari (University of Twente, Vrije Universiteit Amsterdam)
Tom Knop (University of Twente)
Wiendelt Steenbergen (University of Twente)
N. Bhattacharya (TU Delft - Optical Technologies)
A. Chizari (University of Twente, TU Delft - Optical Technologies)
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Abstract
Optical wearable sensors rely on photoplethysmography (PPG) and speckle-plethysmography (SPG) signals to estimate cardiovascular biomarkers, yet the impact of external contact pressure on signal quality during sensor design remains underexplored. We developed a mounting system based on a spring-screw mechanism to apply controlled external contact pressure (20–180 mmHg) to the fingertips of healthy adult volunteers and recorded reflection-mode PPG signals at 660 ± 20 nm. Increasing external contact pressure amplified the systolic peak, dicrotic notch, and diastolic peak by factors of 2.5, 5, and 2, respectively. Our findings show that contact pressure strongly affects PPG morphology and should be optimized to balance comfort with signal quality, enhancing the reliability of wearable cardiovascular monitoring.
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