System design for organic pulse oximeter

Abstract

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.

Monitoring of Vital Signs with Flexible and Wearable Medical Devices

“…The oxygenation is derived from the ratio of the photodetector signal upon excitation at each wavelength and the known molar absorptivity of oxy-and deoxy-hemoglobin at each wavelength. [ 6,83,84 ] In transmission pulse oximetry, one LED has a peak wavelength at which oxy-hemoglobin has a higher absorptivity than deoxy-hemoglobin, and the other LED has a peak wavelength at which oxy-hemoglobin has a lower absorptivity than deoxyhemoglobin. The light from each LED is absorbed by blood, skin, and other tissues before it reaches the photodetector.…”

“…[ 28 ] Next, depending on the frequency of interest (Table 3 ), high-pass, low-pass, or band-pass fi lters can be implemented to extract the desired signal. [ 6,27,84 ] After that, the signal is brought up to a level so that it can be read with ADCs; here the resolution of the ADC should be selected considering the signal range and signal to noise ratio (SNR). The digitized signal is processed by the MCU/MPU-the sampling frequency should be high enough to reduce aliasing.…”

Inkjet‐Printed Flexible Gold Electrode Arrays for Bioelectronic Interfaces

“…[ 4 ] Flexible electronics and optoelectronics are highly promising for creating high-fi delity bioelectronic and biophotonic interfaces. [5][6][7][8] The elasticity of fl exible electronics allows skin-like devices, which are bendable and stretchable. [ 9,10 ] Hence, medical devices fabricated using fl exible materials have the potential to interface better with the human body when compared to rigid electronics.…”

Highly Efficient Ternary Near-Infrared Organic Photodetectors for Biometric Monitoring

“…These performance characteristics are among the best ever reported for an NIR OPD . To prove the practicality of this concept, we applied our OPD in non-invasive human blood oxygen-monitoring biometric devices. , …”

“…24 To prove the practicality of this concept, we applied our OPD in non-invasive human blood oxygen-monitoring biometric devices. 27,28 ■…”