Self-powered, multifunctional, and skin-compatible electronic-tattoos based on hybrid bio-nanomaterials as electrically functionalized skins

Abstract

Electronic tattoos (E-tattoos), imparting electrical functions to skin imperceptibly, are attractive for future biomedical engineering applications. However, it is still challenging to implement all requirements such as biocompatibility, skin-adhesion, breathability, self-powering, etc. in a single E-tattoo for a seamless human–device interface. Here, we report hybrid biomaterial-based E-tattoos fabricated by incorporating graphene with silk sericin (SS)-loaded cellulose nanofibers (CNFs), leveraging each other's strengths for skin-compatible and multifunctional operations. Graphene/SS/CNF E-tattoos show stable and high electrical conductivities under mechanical deformations, along with breathability. Due to SS, strong skin-adhesion is possible without skin irritation. The broadband optical absorption and temperature-dependent conductivity of graphene facilitate optically and electrically stimulated heat patches and temperature sensors. Furthermore, skin-compatibility enables skin-activated self-powering operation via triboelectricity. A substantial open circuit voltage of 320 ± 20 V and power density of 7.2 mW/cm2, sufficient to turn-on light-emitting diodes, are achieved, and self-powered sensory systems can be developed owing to flexible and porous traits of the E-tattoo. The E-tattoo platform, serving as a proof of concept, demonstrates its utility in healthcare and secure communications by enabling Morse code transmission and biomechanical movement detection. This innovative hybrid biomaterial-based E-tattoo can significantly boost healthcare monitoring and secure communication.