Graph theoretical design of biomimetic aramid nanofiber composites as insulation coatings for implantable bioelectronics

Abstract: Creating an insulation material combining crack and delamination resistance, mechanical flexibility, strong adhesion, and biocompatibility is vital for implantable bioelectronic devices of all types. Here, we describe a nanocomposite material addressing these technological challenges that have been designed using blueprints from biomaterials that combine a similar set of properties. These composites are based on aramid nanofibers (ANFs), whose mechanical properties are complemented by the epoxy resins with strong adhesion to various surfaces. The nanoscale structure of the ANF/epoxy nanocomposite coating replicates the nanofibrous organization of human cartilage, which is known for its exceptional toughness and delamination resistance. The structural analogy between percolating networks of cartilage and ANF was demonstrated numerically using graph theory (GT) analysis. The match of multiple GT indexes indicated the near-identical organization pattern of cartilage and ANF/epoxy nanocomposite. When compared with the standard insulating material for bioelectronics, Parylene C, the ANF/epoxy nanocomposite exceeds its performance characteristics in respect to delamination resistance, interfacial adhesion, tissue biocompatibility, electrode cross-talk and inflammatory response. This study opens the possibility of GT-informed design of high-performance insulation materials suitable for different types of electronics for neural engineering and other biomedical applications. GT analysis also makes possible structural characterization of complex biological and biomimetic materials. While the design of the electronics for implantable devices has substantially advanced, the materials for their long-term insulation have not. Delamination of insulation materials constantly results in device failure. The essential problem of this field is finding a material that affords the combination of multiple contrarian properties that need to be resolved to afford future advances in this area. Here, we report a new nanocomposite material that combines durability, toughness, and flexibility, as well as excellent adhesion, biocompatibility, and low inflammatory response. This study opens the road for a large family of materials suitable for different types of implantable electronics for neural engineering and other biomedical applications. Graphic abstract: [Figure not available: see fulltext.]