Flexible and Robust 3D a‐SiGe Radial Junction Near‐Infrared Photodetectors for Rapid Sphygmic Signal Monitoring

Abstract

Flexible near‐infrared (NIR) photodetectors (PDs) are desired for accurate heart rate monitoring, based directly on arterial‐blood‐volume‐change detection, instead of indirect oximetry technology. In this work, a robust 3D construction of flexible a‐SiGe:H p‐i‐n radial junction (RJ) PDs is explored directly upon soft Al foils, working at NIR wavelength 800 nm, which has the highest skin transparency and the least absorption difference from oxyhemoglobin and deoxyhemoglobin variation. The 3D a‐SiGe:H RJ‐PDs demonstrate excellent flexibility and mechanical stability that can undergo 1000‐times bending to 10 mm radius, with a high responsivity of ≈140 mA W−1@800 nm and rise/fall time scales of 5.4 µs/17.6 µs (3.6 µs/13.2 µs before bending). Successful photoplethysmography (PPG) detection of sphygmic signals is achieved at the wrist with significant arterial blood volume changes, working in reflectance mode and using a single NIR source @800 nm. These unique capabilities, enabled by the a‐SiGe:H RJ, have a promising potential to establish a reliable and convenient PPG detection technology, which can help to extract the heartbeat via solely arterial blood volume change, as a complementary and potentially very useful new diagnostic dimension for efficient and accurate real‐time health monitoring.

Flexible photoplethysmographic sensing devices for intelligent medical treatment

“…5d–f). 75 Owing to the mechanical advantages of the radial structure, the device has good flexibility and mechanical stability, which is sufficient to withstand 1000 continuous bending cycles with a bending curvature of 10 mm. 75 Meanwhile, the device has a superior response time (5.4/17.6 μs) and high sensitivity of 140 mA W −1 (at 800 nm) to meet the monitoring requirements associated with PPG signal recordings at human wrists at 655 nm, 520 nm and 800 nm.…”

Skin-Attachable Sensors for Biomedical Applications

“…3 b). Zhang et al [ 40 ] developed a 3D hydrogenated amorphous silicon germanium radial junction PD on Al foil substrates, which allowed good signal monitoring at the wrist.…”

Ultraviolet Photodetectors Based on Polymer Microwire Arrays toward Wearable Medical Devices

“…To avoid skin diseases induced by excess UV exposure, noninvasive UV photodetectors have generated substantial interest in the domains of medical health monitoring and disease regulation through recognizing real-time continuous physiological relevant indicators. − More generally, a wearable UV photodetector with quick and accurate response for the UV exposure in real-time facilitates various medical applications, such as bioimaging techniques and skin disease diagnostics, − yet which are impractical for the current rigid silicon-based medical optoelectronic devices. In particular, epidermal and biomedical UV image sensing system that can precisely collect and measure static and dynamic signals of human bodies with accurate measurement reliability and high patient compliance are vitally important for advanced health care. , The perceived and continuous recognition function for vivo image information warrant stable photodetection performance and highly responsive properties of the image sensing component. , Meanwhile, the flexibility of the UV photodetectors is another imperative feature required to obtain a biocomfortable real-time health monitoring attached firmly to the curved human skin surface. , For suitable medical wearable devices, the mechanical flexibility, portability, and biocompatibility between the electronic components and soft skin can avoid errors in data acquisition and motion artifacts . However, the compatible problems of patterning integration methods with flexible plastic substrates impede the further improvement of medical wearable photodetection applications.…”

“…27,28 Meanwhile, the flexibility of the UV photodetectors is another imperative feature required to obtain a biocomfortable real-time health monitoring attached firmly to the curved human skin surface. 29,30 For suitable medical wearable devices, the mechanical flexibility, portability, and biocompatibility between the electronic components and soft skin can avoid errors in data acquisition and motion artifacts. 31 However, the compatible problems of patterning integration methods with flexible plastic substrates impede the further improvement of medical wearable photodetection applications.…”