Figure 1.

Wearable optical sensors for measuring of human physiology: (a) Miniaturized battery-free NFC enabled wireless systems for wearable pulse oximetry (unencapsulated device and device during operation mounted on a thumbnail) [12]; (b) Ultra-flexible organic PPG sensor attached to finger (smart e-skin system) [13]; (c) Printed reflectance oximeter array composed of four red and IR OLEDs and eight OPDs placed on the forearm for 2D oxygenation mapping [14]; (d) Contactless infrared medical grade thermometer composed from 16 IR sensors for forehead measurement with smartphone connectivity [15]; (e) Battery-free skin UV exposure tracker in form of fashion clip button with smartphone connectivity [16]; (f) Smart glasses with thermal camera for precise temperature measurement and scanning ideal for medical, industrial, and environmental use [17]; (g) Respiration belt with embedded silica fiber optical sensor for thoracic movement analysis [18]; (h) Self-assembled wavy optical microfiber for stretchable wearable sensor (schematic diagram and sensor stuck on the wrist) for monitoring of radial artery pulse wave [19]; (i) Optical fiber interferometer based breathing sensor built into oxygen mask [20]; (j) Skin-interfaced microfluidic battery-free systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat [21]; (k) Contact lens integrated glucose monitoring using smartphones [22]; (l) Skin-wearable fluorometric microfluidic device (emitted by blue light) for measuring of Cl, Na and Zn sweat concentrations [23].