仿生框架诱导矿化制备多功能人工珍珠母

天然珍珠母具备精巧的跨尺度多级结构和优异的力学性能,是目前研究最多的生物结构材料之一,它为高断裂韧性的人工结构陶瓷的设计和制造提供了灵感。然而,为了满足多样化的应用需求,先进结构材料除了要具备优异的机械性能(如强度、硬度和韧性)外,还必须具有多功能特性。本文基于框架诱导矿化方法制备了多种人工珍珠母,通过文石和纳米颗粒的共矿化将具有不同内在功能的纳米颗粒引入基元片中,除了增强的机械性能外,所获得的人工珍珠母材料还根据纳米粒子的类型表现出不同的功能。为了扩展该策略,还分析了具有不同尺寸和电性的纳米粒子对共矿化的影响。这种通用策略可以应用于其他类型的功能化仿生结构陶瓷的制备,这些陶瓷在生物医学等各个领域都有潜在的应用。

Biomimetic chitin hydrogel via chemical transformation

Chitin hydrogel has been recognized as a promising material for various biomedical applications because of its biocompatibility and biodegradability.However,the fabrication of strong chitin hydrogel remains a big challenge because of the insolubility of chitin in many solvents and the reduced chain length of chitin regenerated from solutions.We herein introduce the fabrication of chitin hydrogel with biomimetic structure through the chemical transformation of chitosan,which is a water-soluble deacetylated derivative of chitin.The reacetylation of the amino group in chitosan endows the obtained chitin hydrogel with outstanding resistance to swelling,degradation,extreme temperature and pH conditions,and organic solvents.The chitin hydrogel has excellent mechanical properties while retaining a high water content(more than 95 wt.%).It also shows excellent antifouling performance that it resists the adhesion of proteins,bacteria,blood,and cells.Moreover,as the initial chitosan solution can be feasibly frozen and templated by ice crystals,the chitin hydrogel structure can be either nacre-like or wood-like depending on the freezing method of the precursory chitosan solution.Owing to these anisotropic structures,such chitin hydrogel can exhibit anisotropic mechanics and mass transfer capabilities.The current work provides a rational strategy to fabricate chitin hydrogels and paves the way for its practical applications as a superior biomedical material.

Iron oxide/CNT-based artificial nacre for electromagnetic interference shielding

Biological structural materials,despite consisting of limited kinds of compounds,display multifunctionalities due to their complex hierarchical architectures.While some biomimetic strategies have been applied in artificial materials to enhance their mechanical stability,the simultaneous optimization of other functions along with the mechanical properties via biomimetic designs has not been thoroughly investigated.Herein,iron oxide/carbon nanotube(CNT)-based artificial nacre with both improved mechanical and electromagnetic interference(EMI)shielding performance is fabricated via the mineralization of Fe_(3)O_(4)onto a CNTincorporated matrix.The micro-and nano-structures of the artificial nacre are similar to those of natural nacre,which in turn improves its mechanical properties.The alternating electromagnetic wave-reflective CNT layers and the wave-absorptive iron oxide layers can improve the multiple reflections of the waves on the surfaces of the reflection layers,which then allows sufficient interactions between the waves and the absorption layers.Consequently,compared with the reflection-dependent EMI-shielding of the non-structured material,the artificial nacre exhibits strong absorption-dependent shielding behavior even with a very low content of wave-absorptive phase.Owing to the high mechanical stability,the shielding effectiveness of the artificial nacre that deeply cut by a blade is still maintained at approximately 70%−96%depending on the incident wave frequency.The present work provides a new way for designing structural materials with concurrently enhanced mechanical and functional properties,and a path to combine structural design and intrinsic properties of specific materials via a biomimetic strategy.

Nanograded artificial nacre with efficient energy dissipation

The renowned mechanical performance of biological ceramics can beattributed to their hierarchical structures,wherein structural features atthe nanoscale play a crucial role.However,nanoscale features,such asnanogradients,have rarely been incorporated in biomimetic ceramicsbecause of the challenges in simultaneously controlling the materialstructure at multiple length scales.Here,we report the fabrication of artificial nacre with graphene oxide nanogradients in its aragonite plateletsthrough a matrix-directed mineralization method.The gradients areformed via the spontaneous accumulation of graphene oxide nanosheetson the surface of the platelets during the mineralization process,whichthen induces a lateral residual stress field in the platelets.Nanoindentation tests and mercury intrusion porosimetry demonstrate that the material's energy dissipation is enhanced both intrinsically and extrinsicallythrough the compressive stress near the platelet surface.The energydissipation density reaches 0.159±0.007 nJ/μm^(3),and the toughnessamplification is superior to that of the most advanced cer amics.Numer-ical simulations also agree with the finding that the stress field not ablycontributes to the overall energy dissipation.This work demonstratesthat the energy dissipation of biomimetic ceramics can be furtherincreased by integrating design principles spanning multiple scales.This strategy can be readily extended to the combinations of other struc-tural models for the design and fabrication of structural ceramics withcustomized and optimized performance.