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Nature:以关节软骨为模板的一种水凝胶

摘要 : 材料设计绝大多数情况下都是关注有吸引力的相互作用,如基于聚合物的先进复合材料就是利用无机填料与聚合物基质之间的相互作用。静电排斥也可以被加以利用来产生好的效果,覆盖形成关节的骨头两端的关节软骨就说明了这一点,它们能提供几乎没有摩擦的机械运动。

 材料设计绝大多数情况下都是关注有吸引力的相互作用,如基于聚合物的先进复合材料就是利用无机填料与聚合物基质之间的相互作用。静电排斥也可以被加以利用来产生好的效果,覆盖形成关节的骨头两端的关节软骨就说明了这一点,它们能提供几乎没有摩擦的机械运动。

刘明杰(音译)及同事以这种软骨作为模型,开发出一种水凝胶,它的机械性质由嵌入在其内的带负电的钛酸盐纳米层之间的排斥力主导。该材料当受到与纳米层平行的剪切力作用时很容易变形,但却能抵抗正交施加的压缩力。这种类型的复合材料应能为开发具有不寻常功能的软材料开启新的可能性。

原文链接:

An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets

Machine technology frequently puts magnetic or electrostatic repulsive forces to practical use, as in maglev trains, vehicle suspensions or non-contact bearings1, 2. In contrast, materials design overwhelmingly focuses on attractive interactions, such as in the many advanced polymer-based composites, wher inorganic fillers interact with a polymer matrix to improve mechanical properties. However, articular cartilage strikingly illustrates how electrostatic repulsion can be harnessed to achieve unparalleled functional efficiency: it permits virtually frictionless mechanical motion within joints, even under high compression3, 4. Here we describe a composite hydrogel with anisotropic mechanical properties dominated by electrostatic repulsion between negatively charged unilamellar titanate nanosheets5 embedded within it. Crucial to the behaviour of this hydrogel is the serendipitous discovery of cofacial nanosheet alignment in aqueous colloidal dispersions subjected to a strong magnetic field, which maximizes electrostatic repulsion6 and thereby induces a quasi-crystalline structural ordering7, 8 over macroscopic length scales and with uniformly large face-to-face nanosheet separation. We fix this transiently induced structural order by transforming the dispersion into a hydrogel9, 10 using light-triggered in situ vinyl polymerization11. The resultant hydrogel, containing charged inorganic structures that align cofacially in a magnetic flux12, 13, 14,15, 16, 17, 18, 19, deforms easily under shear forces applied parallel to the embedded nanosheets yet resists compressive forces applied orthogonally. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, inspired by articular cartilage, will open up new possibilities for developing soft materials with unusual functions.(doi:10.1038/nature14060)

Materials science: Like cartilage, but simpler

The properties of articular cartilage, which lines bones in joints, depend partly on repulsion between components of the material. A new synthetic gel that mimics this feature has rare, direction-dependent properties.(doi:10.1038/517025a)

对应Nature杂志: 2015年01月01日Nature杂志精选

来源: Nature 浏览次数:65

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