Abstract: Graphene is a 2D nanocomposite that has been gaining popularity in the research community in recent years. It is light weight with high tensile strength and excellent electrical conductivity. While graphene nanosheets are typically assembled into macroscopic nanocomposites, their beneficial properties may degrade from the aggregation of nanosheets owing to the weak interfacial interactions caused by random orientation and many other obstacles. Thus, finding an effective way to assemble the graphene nanosheets while not impacting its intrinsic properties is challenging. In nature, live organisms have always assembled numerous nanomaterials into high-performance nanocomposites. For example, nacre is composed of aragonite nanoplatelets and biopolymers such as protein and chitin. The aragonite nanoplatelets with a 95% volume fraction are stacked into a layered structure and "glued" together by biopolymers based on the "brick-and-mortar" architecture. The fracture toughness is 3000 times higher than natural aragonite minerals owing to the "extrinsic toughening mechanism" from the crack deflection and bridging in the "brick-and-mortar" architecture. We propose a nacre-inspired layered structure in graphene-based nanocomposites with two complementary strategies:constructing nacre-like and inverse nacre-like structures. This paper first introduces the structure and toughening mechanism of nacre and clarify the advantages of a bioinspired strategies. Then, some of the recent work on nacre-inspired graphene-based multifunctional nanocomposites is discussed. To construct the nacre-like structure, we fabricated graphene-based fibers and membranes with graphene as the main component. The nacre-like graphene-based nanocomposites have excellent tensile strength and toughness due to the synergistic effects from interfacial interactions and building blocks. It also demonstrated high electrical conductivity, which makes it suitable for electromagnetic interference shielding or supercapacitors. We also fabricated inverse nacre-like graphene-based nanocomposites with a small amount of graphene. The inverse nacre-like graphene-based nanocomposites has a layered structure and exhibited the "extrinsic toughening mechanism" seen in nacre. Consequently, the inverse nacre-like graphene-based nanocomposites possesses high fracture toughness that pushes the limit of "mixing rule". With the addition of graphene, the inverse nacre-like nanocomposites are suitable for use in many applications such as electrical conductivity, electrical heating, temperature measurement and many other functions. Finally, our study summarizes the strategies to overcome the obstacles we encountered during the assembly process to construct both the nacre-like and inverse nacre-like structures that were based on graphene. Some of the challenges we encountered include the small sample size, the quality of graphene nanosheets and developing hierarchical assembly techniques. The upcoming trends in nacre-inspired graphene-based multifunctional nanocomposites will also be discussed.

Key words: Nacre, Bioinspiration, Graphene, Multifunction, Nanocomposite