Biocompatible Reduced Graphene Oxide Ink Hybridized by Wool Keratin for Flexible Strain Sensor Electronics

Ink based on nanoconductive materials can achieve the scalable fabrication of flexible devices. Nanocarbon materials, such as reduced graphene oxide (rGO), graphene oxide (GO), and carbon nanotubes (CNT), offer great potential in the field of flexible electronics. However, these materials are challenging to use in inks, especially environmentally friendly water-soluble inks, due to their poor dispersion in most solvents. In this study, a biocompatible and well-dispersed keratin-based rGO ink was fabricated consisting of keratin extracted from waste wool and rGO. The resulting noncovalent interactions, such as hydrogen bonds, pi-pi stacking interaction, and van der Waals forces, realized good dispersion. As an application demonstration, a flexible strain sensor was prepared by using keratin-based rGO ink, and the results demonstrated that this sensor exhibited good sensitivity (gauge factor (GF), up to 3696) and stability and could be used to monitor human health, such as pulse and abdominal breathing, as well as realize human-computer interactions such as an artificial control manipulator successfully grasping objects. Accordingly, we demonstrated a way of high-quality utilization of waste wool and the significant potential of keratin-based rGO ink-prepared waste wool in intelligent wearable devices, human-computer interaction devices, and smart living applications.