. Author manuscript; available in PMC: 2020 Jul 29.

Published in final edited form as: Nat Rev Mater. 2020 Jan 7;5(2):149–165. doi: 10.1038/s41578-019-0167-3

Table 2 |.

Types, working principles and applications of implantable and wearable photonic devices for smart healthcare

Device	Main mechanism	Working principle	Applications	Refs
*Implantable photonic devices*
Health-monitoring device	Pulse oximetry	Comparison of the optical absorption of Hb and HbO₂	Monitoring neural behaviour	¹⁰⁵
Health-monitoring device	Optical resonance of cavity structure	Monitoring the reflected resonance peak shift via the distance change of the optical cavity caused by IOP	IOP monitoring	¹⁰⁶
Photodynamic device	Photonic ROS generation	Photosensitizers generate ROS for cancer therapy	Cancer therapy	^107,108
Optogenetic device	Optogenetics	Genetically modified cells express light-sensitive ion channels	Treatment of diabetes, brain, peripheral nerve and bladder diseases	^{19–22,114,128}
*Wearable photonic devices*
Contact lens	Structural colour change of photonic crystal	Volume change resulting from the binding of glucose to boronic acid	Tear glucose level monitoring	^158,160,161
	Structural colour change of photonic crystal	Volume change resulting from drug release from the lens	Ocular drug-release monitoring	¹⁶²
	Colorimetric change of glucose reagents	Optical change resulting from the binding of glucose to boronic acid or concanavalin A	Tear glucose level monitoring	^163–166
	Diffuse reflection of NIR light	Light scattering depending on the glucose concentration change in ocular blood vessels	Blood glucose level monitoring	¹⁶⁹
Smart glasses	Photoreceptor stimulation	Modulating hormone secretion with blue-light LEDs	SAD and circadian rhythm control	^182–184
Skin patch	Pulse oximetry	Comparison of the optical absorption of Hb and HbO₂	SpO₂ level monitoring	^142,143,187, ^188,190,191
	Photoplethysmography	Detecting the volumetric change of peripheral blood	Cardiac function monitoring	^145,189
	Photobiomodulation	Stimulating mitochondrial chromophores for cell proliferation	Wound healing, skin care and hair growth	^194,195

Hb, haemoglobin; HbO₂, oxygenated haemoglobin; IOP, intraocular pressure; LED, light-emitting diode; NIR, near infrared; ROS, reactive oxygen species; SAD, seasonal affective disorder; SpO₂, saturation of peripheral oxygen.