Paper: A promising material for human-friendly functional wearable electronics

The ever-growing overlap between electronics and wearable technology is driving the demand for utilizing novel materials that are cost-effective, light-weight, eco-friendly, mechanically deformable and can be conformably and comfortably worn on human body as substrate to support the reliable operation of wearable electronic functionalities. Paper materials comprised of bio-origin ingredients (e.g., cellulose and carbon derivatives) have recently attracted remarkably increasing research and commercial interests for prototyping next-generation wearable electronics due to their superiorities including natural abundance, flyweight, mature manufacturing process, specific structural properties, favorable mechanical bendability, biocompatibility and nontoxicity over their counterparts. Feasibility of engaging paper materials has been proved by outstanding performances in body-worn healthcare sensing systems, electro-stimulated artificial muscles, on-site memory storage and wearable power supply on paper substrate. In this review, we present a state-of-the-art introduction of diverse paper substrate options and fabrication techniques employed for realizing paper electronics, and discuss both pros and cons of each manufacturing tactic. Additionally, we summarize developing trends of paper-based electronics in the emerging wearable applications. Based upon these, final conclusions, encountering challenges, accompanied with advancing outlooks are illustrated.