3D Printed Flexible Photoplethysmography Sensor Array for Tissue Oximetry

Recently there has been a trend to use the optoelectronic system of pulse oximeters, a photodiode and a pair of light emitting diodes of different wavelengths, to perform elementary tissue oximetry by measuring the changes in oxygenated and deoxygenated haemoglobin concentrations in tissues. This paper presents introductory work into how an affordable flexible array of such tissue oximeters could be manufactured by using direct-write 3D printing and commercial surface mount devices. For this purpose, a flexible printed circuit board was fabricated by printing 30 wt. % silver nanoparticle ink on 60 mu m polyimide film. An array of photoplethysmography (PPG) sensors was made by combining the circuit board with two pairs of 660 nm and 940 nm light emitting diodes and six photodiodes. It was demonstrated how this combination of optoelectronic devices results in a 2-by-4 array of PPG sensors with capability to simultaneously measure PPG signals with multiple photodiodes. It was concluded that further work must be completed to evaluate the possibility of this sensor array to be used for tissue oximetry.