Fiber-based quantum-dot pulse oximetry for wearable health monitoring with high wavelength selectivity and photoplethysmogram sensitivity

Abstract

Increasing demand for real-time healthcare monitoring is leading to advances in thin and flexible optoelectronic device-based wearable pulse oximetry. Most previous studies have used OLEDs for this purpose, but did not consider the side effects of broad full-width half-maximum (FWHM) characteristics and single substrates. In this study, we performed SpO2 measurement using a fiber-based quantum-dot pulse oximetry (FQPO) system capable of mass production with a transferable encapsulation technique, and a narrow FWHM of about 30 nm. Based on analyses we determined that uniform angular narrow FWHM-based light sources are important for accurate SpO2 measurements through multi-layer structures and human skin tissues. The FQPO was shown to have improved photoplethysmogram (PPG) signal sensitivity with no waveguide-mode noise signal, as is typically generated when using a single substrate (30–50%). We successfully demonstrate improved SpO2 measurement accuracy as well as all-in-one clothing-type pulse oximetry with FQPO.

Wearable and Wavelength-Tunable Near-Infrared Organic Light-Emitting Diodes for Biomedical Applications

“…The images of the electrodes utilized in the analysis are shown in Figure S1 of the Supporting Information. The microcavity effect is influenced by a range of factors, including the electrode’s reflectance and transmittance, as well as the distance between each electrode, i.e., the overall thickness of the organic layer . The light generated internally within the OLED was reflected between the Ag and Al electrodes, and the constructive interference induced by light possessing identical phases amplified the magnitude of a particular wavelength.…”

Quantum-Dot Light-Emitting Fiber Toward All-In-One Clothing-Type Health Monitoring

“…To compare the optical characteristics of the fabricated 1D fiber-based QDLEF with those of a 2D substrate-based planar QDLED, red and green QDLEDs were fabricated using a transferable encapsulation technique reported in previous research. 22 The structure of these QDLEDs can be seen in Figure S2a,b, and the basic structure was the same as the 1D fiber-based QDLEFs. Additionally, to maintain a consistent area, we set the width of the QDLED to 250 μm (Figure S2a).…”

“…This leads to lower accuracy in SpO 2 monitoring, which affects the diagnostic reliability of the pulse oximeter. 22 In other words, a practical exploration is needed of the advantages of flexible and narrow FWHM light sources in pulse oximetry sensor.…”

Structural and Material-Based Approaches for the Fabrication of Stretchable Light-Emitting Diodes

“…Therefore, placing active layers composed of high modulus materials on the neutral mechanical plane can mitigate device failures caused by material damage, such as fractures. By optimizing the thickness of top/bottom passivation layers (or substrates), the location of neutral mechanical planes can be adjusted [ 74 , 75 ].…”