Printable Photonic Materials and Devices for Smart Healthcare.

Photonic materials possess tunable optical properties and have been widely utilized for healthcare applications. These materials enable the detection of physical and physiological bio-signals via modulated optical output characteristics, such as wavelength shifts, fluorescence emission, and light scattering. When further synthesized into functional photonic inks, multimodal devices for epidermal, minimally invasive, and implantable bio-sensing can be constructed in facile and printable manners. This review first introduces functional photonic materials in different geometries and their unique properties. To enable feasible fabrication of multi-functional photonic devices for biosensing in versatile platforms, the synthesis of printable inks and the as-printed devices are then illustrated. Subsequently, the advances and breakthroughs to construct printable photonic devices and integrated systems for wearable and implantable applications are displayed, especially for multimodal sensing to facilitate personalized and remote healthcare. Finally, the challenges in achieving mechanical stability, eliminated degradation, enhanced biocompatibility in dynamic biological environments, and scalable production are discussed, along with the prospects toward reliable and intelligent healthcare.