Organic Multi-Channel Optoelectronic Sensors for Wearable Health Monitoring

Abstract

Recent progress in printed optoelectronics and their integration in wearable sensors have created new avenues for research in reflectance photoplethysmography (PPG) and oximetry. The reflectionmode sensor, which consists of light emitters and detectors, is a vital component of reflectance oximeters. Here, we report a systematic study of the reflectance oximeter sensor design in terms of component geometry, light emitter and detector spacing, and the use of an optical barrier between the emitter and the detector to maximize sensor performance. Printed red and near-infrared (NIR) organic light-emitting diodes (OLEDs) and organic photodiodes (OPDs) are used to design three sensor geometries: (1) Rectangular geometry, where square OLEDs are placed at each side of the OPD; (2) Bracket geometry, where the OLEDs are shaped as brackets and placed around the square OPD; (3) Circular geometry, where the OLEDs are shaped as block arcs and placed around the circular OPD. Utilizing the bracket geometry, we observe 39.7% and 18.2% improvement in PPG signal magnitude in the red and NIR channels compared to the rectangular geometry, respectively. Using the circular geometry, we observe 48.6% and 9.2% improvements in the red and NIR channels compared to the rectangular geometry. Furthermore, a wearable two-channel PPG sensor is utilized to add redundancy to the measurement. Finally, inverse-variance weighting and template matching algorithms are implemented to improve the detection of heart rate from the multi-channel PPG signals.INDEX TERMS Reflection photoplethysmography sensor, organic optoelectronics, pulse oximetry, wearable sensors, printed electronics, flexible electronics.

OLED Opportunity in Healthcare With the Pulse Oximeter

“…An example of the latter can be found in a 2019 article by the University of California, Berkeley Group ( Fig . ) 4 . In this work, an advanced reflectance type of all‐organic multichannel oximeter was demonstrated.…”

“…Here, mV: millivolts; NIR: near infrared. Reproduced from IEEE Access under the Creative Commons License CC By 4.0 4 …”

Nanostructured Organic/Hybrid Materials and Components in Miniaturized Optical and Chemical Sensors

“…Several reflectance-based sensors have been fabricated for wireless monitoring of the photoplethysmogram (PPG) signal [166]. In particular, Arias' research group, one of the leaders of this research area [161,167,168], exhaustively showed a real-life application of a printed array of OLEDs and OPDs [167]. This was demonstrated through an accurate design of (i) single components, (ii) their relative distances/dimensions, (iii) their electrical connection and (iv) the collection and the analysis of the data.…”

External temperature sensor assisted a new low power photoplethysmography readout system for accurate measurement of the bio-signs

“…The long-time-continuous monitoring of the bio-sign using PPG devices is always a challenge because these devices are suffered from the mispositioning, low signal to noise ratio (SNR). In addition, PPG based devices are highly affected by the motion artifact and ambient noise artifact (Khan et al 2019), temperature variation and the skin color (Khan et al 2015;Pandey et al 2019). Usually the AC/DC ratio associated with LED-PD PPG sensors are less than 10%.…”

“…Considering all the above mention challenges associated with the PPG sensors, in the recent past, many researchers have dedicated their effoert to developed a long time continuous and accurate measurement of the bio sign using the PPG devices (Wu et al 2020;Marefat et al 2020;Lin et al 2019). Khan et al (2019) proposed a flexible organic sensor for the health monitoring. A rectangular, bracket and circular geometry were design to achieve the improved the AC/DC.…”