System design for organic pulse oximeter

Wearable medical devices that would benefit from mechanical flexibility and new form factors represent a great shift in direction of research in the field of printed electronics. The minimal functionality desired from wearable medical devices is the monitoring of vital signs. Pulse rate and blood oxygenation are considered primary vital signs that help to evaluate the general physical health of a person. The methods used to measure pulse rate and blood oxygenation with sensors based on organic light-emitting diodes (OLEDs) and organic photodiodes (OPDs) are reported here. Departing from the conventional practice of using red (630 nm) and infrared (940 nm) light for measuring pulse oxygenation, we have successfully implemented solution processed red (626 nm) and green (532 nm) OLEDs fabricated from polyfluorene blends in an all-organic optoelectronic pulse oximeter sensor. The red and green OLEDs operate at 9 V, 1 kHz, and transmit light through a human index finger. The transmitted light is sensed by an OPD placed on the opposite side of the finger. After filtering and amplification, the photoplethysmogram (PPG) signal is obtained and used to accurately measure pulse rate and blood oxygenation.