Capillary-bridge–derived particles with negative Gaussian curvature
Capillary-bridge–derived particles with negative Gaussian curvature
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具有负高斯曲率的毛细管桥衍生粒子
DOI：
10.1073/pnas.1424383112
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
T. J. McCarthy
中科院分区：
文献类型：
--
作者：
Liming Wang;T. J. McCarthy
重要性颗粒可用于从化妆品到导电粘合剂的众多应用中。它们可以由不同的物质组成，大小不一，并具有不同的形状，如球体和棒。粒子的表面几乎普遍是凸的（正高斯曲率），原因与液体在空气中形成球体的原因相同。然而，跨越两个表面的液滴形成沙漏形毛细管桥，其在跨越两个表面的维度上具有凹曲率。在这篇文章中，我们表明，单体的毛细管桥可以聚合，制备沙漏形粒子与负高斯曲率。具有这种形状的颗粒尚未被研究。我们报道了通过热聚合液体单体毛细管桥来制备毫米级颗粒，以形成具有负高斯曲率的悬链形颗粒。毛细管桥和所得颗粒的形状可以使用几个可寻址的参数进行微调：（i）跨越的表面上的光刻钉扎特征的形状、尺寸和取向;（ii）相对的支撑表面之间的距离;和（iii）相对特征的横向位移（剪切）。悬链形颗粒由于其凹形的波纹而表现出可控的光学性质，其形状可以容易地操纵。颗粒在冷凝液体（水）的存在下自组装以形成可逆的颈对颈对和不太可逆的端对端聚集体。我们认为，这种方法可以缩小到微米尺寸，通过制造一个阵列的微米级粒子。我们还认为，与动态润湿的讨论，这些颗粒将表现出有趣的各向异性的粘合性能。
Significance Particles find use in a plethora of applications that range from cosmetics to electrically conducting adhesives. They can be composed of different substances, vary in size, and have different shapes such as spheres and rods. The surfaces of particles are almost universally convex (positive Gaussian curvature) for the same reason that liquid forms a sphere in air. A drop of liquid spanning two surfaces, however, forms an hourglass-shaped capillary bridge with concave curvature in the dimension that spans the two surfaces. In this article, we show that capillary bridges of monomers can be polymerized to prepare hourglass-shaped particles with negative Gaussian curvature. Particles with this shape have not yet been studied. We report the preparation of millimeter-scale particles by thermal polymerization of liquid monomer capillary bridges to form catenoid-shaped particles that exhibit negative Gaussian curvature. The shape of the capillary bridges and resulting particles can be finely tuned using several addressable parameters: (i) the shape, size, and orientation of lithographic pinning features on the spanned surfaces; (ii) the distance between opposing support surfaces; and (iii) the lateral displacement (shear) of opposing features. The catenoid-shaped particles exhibit controllable optical properties as a result of their concave menisci, the shape of which can be easily manipulated. The particles self assemble in the presence of a condensing liquid (water) to form reversible neck-to-neck pairs and less reversible end-to-end aggregates. We argue that this approach could be scaled down to micrometer dimensions by fabricating an array of micrometer-scale particles. We also argue, with a discussion of dynamic wetting, that these particles will exhibit interesting anisotropic adhesive properties.