Self-Exfoliation of Flake Graphite for Bioinspired Compositing with Aramid Nanofiber toward Integration of Mechanical and Thermoconductive Properties

Flexible yet highly thermoconductive materials are essential for the development of next-generation flexible electronic devices.Herein,we report a bioinspired nanostructured film with the integration of large ductility and high thermal conductivity based on self-exfoliated pristine graphene and three-dimensional aramid nanofiber network.A self-grinding strategy to directly exfoliate flake graphite into few-layer and few-defect pristine graphene is successfully developed through mutual shear friction between graphite particles,generating largely enhanced yield and productivity in comparison to normal liquid-based exfoliation strategies,such as ultrasonication,high-shear mixing and ball milling.Inspired by nacre,a new bioinspired layered structural design model containing three-dimensional nanofiber network is proposed and implemented with an interconnected aramid nanofiber network and high-loading graphene nanosheets by a developed continuous assembly strategy of sol-gel-film transformation.It is revealed that the bioinspired film not only exhibits nacre-like ductile deformation behavior by releasing the hidden length of curved aramid nanofibers,but also possesses good thermal transport ability by directionally conducting heat along pristine graphene nanosheets.

Additive manufacturing of NiTi lightweight porous structures bio-mimicking coral skeleton with enhanced mechanical properties and shape memory functions

Concerning the high demand for lightweight and multifunctional properties of engineering structures, the coral skeleton-inspired sheet-based(CSS) structure, which was a novel bio-mimicking coral skeleton wall-septa architecture with a unique ability to resist wave shocks was fabricated using NiTi alloy by laser powder bed fusion(LPBF) technology. The effects of laser energy density(LED) on surface morphologies, microstructures, phase transformation behavior, and mechanical properties of LPBFfabricated CSS structures were systematically investigated. The results indicated that the size deviation was predominantly governed by powder adhesion and step effect. NiTi CSS structures with LED of 71 J·mm~(-3)possessed superior compressive modulus(~400 MPa), ultimate strength(~13 MPa), and energy absorption efficiency(~69%). The compression fracture mechanism of the LPBF-fabricated NiTi CSS structures was revealed to be predominantly brittle fracture accompanied by ductile fracture. Furthermore, the Ni_4Ti_3 nanoprecipitates induced the precipitation strengthening effect, enabling better shape memory response at LED of 71 J·mm~(-3), with a recoverable strain of 3.63% and recovery ratio of 90.8%, after heating under a pre-strain of 4%. This study highlights the importance of a bionic design strategy for enhancing the mechanical properties of NiTi components and offers the possibility to tailor its functional properties.

Synthesis of Biomimetic Superhydrophobic Surface through Electrochemical Deposition on Porous Alumina

The superhydrophobicity of plant leaves is a benefit of the hierarchical structures of their surfaces. These structures have been imitated in the creation of synthetic surfaces. In this paper, a novel process for fabrication of biomimetic hierarchical structures by electrochemical deposition of a metal on porous alumina is described. An aluminum specimen was anodically oxidized to obtain a porous alumina template, which was used as an electrode to fabricate a surface with micro structures through electrochemical deposition of a metal such as nickel and copper after the enlargement of pores. Astonishingly, a hier- archical structure with nanometer pillars and micrometer clusters was synthesized in the pores of the template. The nanometer pillars were determined by the nanometer pores. The lbrmation of micrometer clusters was related to the thin walls of the pores and the crystallization of the metal on a flat surface. From the as-prepared biomimetic surfaces, lotus-leaf-like superhydrophobic surfaces with nickel and copper deposition were achieved.

Bioinspired laminated bioceramics with high toughness for bone tissue engineering

For the research of biomaterials in bone tissue engineering,it is still a challenge to fabricate bioceramics that overcome brittleness whilemaintaining the great biological performance.Here,inspired by the toughness of naturalmaterials with hierarchical laminated structure,we presented a directional assembly-sintering approach to fabricate laminated MXene/calcium silicate-based(L-M/CS)bioceramics.Benefiting from the orderly laminated structure,the LM/CS bioceramics exhibited significantly enhanced toughness(2.23MPa·m^(1/2))and high flexural strength(145MPa),which were close to the mechanical properties of cortical bone.Furthermore,the L-M/CS bioceramics possessed more suitable degradability than traditional CaSiO_(3)bioceramics due to the newly formed CaTiSiO_(5)after sintering.Moreover,the L-M/CS bioceramics showed good biocompatibility and could stimulate the expression of osteogenesisrelated genes.The mechanism of promoting osteogenic differentiation had been shown to be related to theWnt signaling pathway.This work not only fabricated calciumsilicate-based bioceramics with excellentmechanical and biological properties for bone tissue engineering but also provided a strategy for the combination of bionics and bioceramics.

Bioinspired PcBN/hBN fibrous monolithic ceramic:High-temperature crack resistance responses and self-lubricating performances

The high strength and toughness of natural materials are mainly determined by a combination of mechanisms operating at different length scales,which can be used as a strategy to reduce the intrinsic brittleness of ceramics.Inspired by the architectures of bamboo,the polycrystalline cubic boron nitride/hexagonal boron nitride(PcBN/hBN)fibrous monolithic ceramics with a long fiber arrangement structure was constructed with PcBN fiber cells and hBN cell boundaries,and its crack resistance responses and tribological performances were investigated.The composite ceramic failed in a non-brittle manner with the rising resistance curve(R-curve)behavior,which was attributed to multiscale crack effects in the hierarchical architecture.The maximum crack growth toughness was extremely high(approximately 21 MPa×m^(1/2)),corresponding to a 270%increase over the crack initiation toughness.Excellent fracture resistance could be retained even above 1000℃.Moreover,the composite ceramic exhibited low and stable friction coefficients(approximately 0.33)when paired with a Si_(3)N_(4)pin at high temperature(1000℃),owing to the lubrication function of hBN cell boundaries with weak van der Waals forces and a small amount of liquid B_(2)O_(3)produced.As a result,a synergistic improvement of mechanical and tribological properties at high temperature(1000℃)was realized by combining bionic structure and tribological design.It provides important theoretical and technical support for expanding the application of self-lubricating composite ceramics in harsh environments.

Biomimetic directional transport for sustainable liquid usage

Through hundreds of millions of evolution,animals and plants have possessed their unique structures to adapt to natural variations.As a familiar process,liquid transportation plays an important part in both production and life,and researchers focus on how to achieve this process in a convenient and efficient way without energy input.Inspired by nature,various bioinspired structures are reported and have won multiple achievements.This review starts from basic theory about surface wettability,and then summarises the creatures with special liquid transport functions as well as crucial structures that cause this phenomenon.Next,the recent articles about transporting liquid by bioinspired materials are introduced.Finally,we proposed a brief conclusion and the prospect of bionic materials in the future.