Skin-Adhesive, -Breathable, and -Compatible Nanopaper Electronics for Harmonious On-Skin Electrophysiological Monitoring

On-skin electronics, which offers an interface for extracting electrophysiological signals from skin, is intensively investigated using electrodes mounted on flexible substrates. Despite numerous efforts toward substrate design to optimize user comfort, substrates with skin-adhesion, skin-breathability, skin-compatibility, mechanical endurance, sterilizability, sustainability, and biodegradability remain desirable candidates for human- and environment-friendly on-skin electronics. To this end, a wood-derived cellulose nanofiber paper (denoted nanopaper) with customized porous nanostructures is developed in this study. The customized porous nanopaper enables water-assisted deformation for skin-conformability, thereby realizing outstanding skin-adhesion force, along with high skin-breathability and compatibility, superior to those of conventional substrates reported for on-skin electronics. By mounting gold electrodes on the porous nanopaper and adhering them to human skin, the real-time monitoring of electroencephalogram, electromyogram, and electrocardiogram for diagnosing the human physiological state is successfully achieved. Furthermore, the gold-electrode-mounted porous nanopaper affords unique characteristics including durability against skin deformation, reusability, and even sterilizability, owing to its high mechanical endurance, and thermal stabilities. Thus, the as-prepared porous nanopaper serves a fascinating platform for human- and environment-harmonious on-skin electronics.