Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK.
National Physical Laboratory, Hampton Road, Teddington TW11 0LW, UK.
Biosensors (Basel). 2018 Mar 29;8(2):33. doi: 10.3390/bios8020033.
Imaging photoplethysmography (iPPG) is an emerging technology used to assess microcirculation and cardiovascular signs by collecting backscattered light from illuminated tissue using optical imaging sensors. The aim of this study was to study how effective smart garment fabrics could be capturing physiological signs in a non-contact mode. The present work demonstrates a feasible approach of, instead of using conventional high-power illumination sources, integrating a grid of surface-mounted light emitting diodes (LEDs) into cotton fabric to spotlight the region of interest (ROI). The green and the red LEDs (525 and 660 nm) placed on a small cotton substrate were used to locally illuminate palm skin in a dual-wavelength iPPG setup, where the backscattered light is transmitted to a remote image sensor through the garment fabric. The results show that the illuminations from both wavelength LEDs can be used to extract heart rate (HR) reaching an accuracy of 90% compared to a contact PPG probe. Stretching the fabric over the skin surface alters the morphology of iPPG signals, demonstrating a significantly higher pulsatile amplitude in both channels of green and red illuminations. The skin compression by the fabric could be potentially utilised to enhance the penetration of illumination into cutaneous microvascular beds. The outcome could lead a new avenue of non-contact opto-physiological monitoring and assessment with functional garment fabrics.
成像光体积描记术（iPPG）是一种新兴技术，通过使用光学成像传感器收集来自照明组织的背散射光来评估微循环和心血管迹象。本研究旨在研究智能服装面料在非接触模式下捕捉生理迹象的有效性。本工作展示了一种可行的方法，即用表面贴装发光二极管（LED）网格代替传统的高功率照明源，将其集成到棉织物中，以突出感兴趣区域（ROI）。在双波长 iPPG 设置中，将放置在小棉基板上的绿色和红色 LED（525 和 660nm）用于局部照明手掌皮肤，背散射光通过服装织物传输到远程图像传感器。结果表明，与接触式 PPG 探头相比，两种波长 LED 的照明都可用于提取心率（HR），准确率达到 90%。在皮肤表面拉伸织物会改变 iPPG 信号的形态，在绿色和红色照明的两个通道中都显示出明显更高的脉动幅度。织物对皮肤的压缩作用可潜在地用于增强照明进入皮肤微血管床的穿透性。该结果可能为使用功能性服装面料进行非接触式光生理监测和评估开辟新途径。
