Park Sungoh, Liu Qingkun, Smalyukh Ivan I
Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Department of Electrical, Computer and Energy Engineering, Soft Materials Research Center and Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2016 Dec 30;117(27):277801. doi: 10.1103/PhysRevLett.117.277801. Epub 2016 Dec 29.
Self-assembly of colloidal particles is poised to become a powerful composite material fabrication technique, but remains challenged by a limited control over the ensuing structures. We develop a new breed of nematic colloids that are physical analogs of a mathematical surface with boundary, interacting with the molecular alignment field without inducing defects when flat. However, made from a thin nanofoil, they can be shaped to prompt formation of self-compensating defects that drive preprogramed elastic interactions mediated by the nematic host. To show this, we wrap the nanofoil on all triangular side faces of a pyramid, except its square base. The ensuing pyramidal cones induce point defects with fractional hedgehog charges of opposite signs, spontaneously align with respect to the far-field director to form elastic dipoles and nested assemblies with tunable spacing. Nanofoils shaped into octahedrons interact as elastic quadrupoles. Our findings may drive realization of low-symmetry colloidal phases.
胶体颗粒的自组装有望成为一种强大的复合材料制造技术，但对由此产生的结构的有限控制仍然是一个挑战。我们开发了一种新型向列胶体，它是具有边界的数学表面的物理类似物，与分子排列场相互作用，在平坦时不会产生缺陷。然而，由薄纳米箔制成，它们可以被塑形以促使形成自补偿缺陷，这些缺陷驱动由向列主体介导的预编程弹性相互作用。为了证明这一点，我们将纳米箔包裹在金字塔的所有三角形侧面上，除了它的正方形底面。由此产生的金字塔形锥体诱导出具有相反符号的分数刺猬电荷的点缺陷，相对于远场指向矢自发排列形成弹性偶极子和具有可调间距的嵌套组件。被塑造成八面体的纳米箔作为弹性四极子相互作用。我们的发现可能推动低对称胶体相的实现。
