Biocompatible and Biodegradable 3D Graphene/Collagen Fiber Hybrids for High-Performance Conductive Networks and Sensors

Polymer-based flexible conductive materials are crucial for wearable electronics, electronic skin, and other smart materials. However, their development and commercial applications have been hampered by the lack of strain tolerance in the conductive network, poor bonding with polymers, discomfort during wear, and a lack of biocompatibility. This study utilized oil-tanned leather with a natural network structure, high toughness, and high tensile deformation recovery as a structural template. A graphene (Gr) conductive network was then constructed on the collagen network of the leather, with coordination cross-linking between Gr and collagen fibers through aluminum ions (Al³⁺). A new flexible conductive material (Al-GL) was then constructed. Molecular dynamics simulations and experimental validation revealed the existence of physical adsorption, hydrogen bonding adsorption, and ligand bonding between Al³⁺, Gr, and collagen fibers. Although we established that the binding sites between Al³⁺ and collagen fibers were primarily on carboxyl groups (-COOH), the mechanism of chemical bonding between Gr and collagen fibers remains unclear. The Al-GL composite exhibited a high shrinkage temperature (67.4 °C) and low electrical resistance (16.1 kΩ·sq^-1), as well as good softness (9.33 mN), biocompatibility, biodegradability (<60 h), and air and moisture permeability. Furthermore, the incorporation of Al³⁺ resulted in a heightened Gr binding strength on Al-GL, and the resistance remained comparable following 1 h of water washing. The Al-GL sensor prepared by WPU encapsulation not only demonstrated highly sensitive responses to diverse motion signals of the human body but also retained a certain degree of response to external mechanical effects underwater. Additionally, the Al-GL-based triboelectric nanogenerator (Al-GL TENG) exhibited distinct response signals to different materials. The Al-GL prepared by the one-pot method proposed in this study offers a novel approach to combining functional nanofillers and substrate materials, providing a theoretical foundation for collagen fiber-based flexible conductive materials.