Departamento de Física da Faculdade de Ciências, Universidade de Lisboa, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa, Portugal and Centro de Física Teórica e Computacional, Universidade de Lisboa, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa, Portugal.
Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2014 Jun 6;112(22):225501. doi: 10.1103/PhysRevLett.112.225501. Epub 2014 Jun 2.
Colloidal crystals belong to a new class of materials with unusual properties in which the big challenge is to grow large-scale structures of a given symmetry in a well-controlled and inexpensive way. Recently, template-assisted crystallization was successfully exploited experimentally in the case of colloidal particles dispersed in isotropic fluids. In liquid crystal (LC) colloids, particles are subjected to long-range anisotropic elastic forces originating from the anisotropic deformation of the underlying order parameter. These effective interactions are easily tunable by external electric or magnetic fields, light, temperature, or confinement and, thus, provide additional handles for better control of colloidal assembly. Here we use the coupling between microsculptured bounding surfaces and LC elasticity in order to guide the self-assembly of large-scale colloidal structures. We present explicit numerical calculations of the free energy landscape of colloidal particles in the presence of convex protrusions modeled as squared pyramids comparable to the size of the particles. We show the existence of strong trapping potentials that are able to efficiently localize the colloidal particles and withstand thermal fluctuations. Three-dimensional optical imaging experiments support the theoretical predictions.
胶体晶体属于一类具有特殊性质的新型材料，其主要挑战是以可控且经济的方式大规模生长具有给定对称性的结构。最近，在各向同性流体中分散的胶体粒子的情况下，实验中成功地利用模板辅助结晶法加以利用。在液晶 (LC) 胶体中，粒子受到源自基础序参量各向异性变形的长程各向异性弹性力的作用。这些有效相互作用很容易通过外部电场或磁场、光、温度或限制来调节，从而为更好地控制胶体组装提供了额外的手段。在这里，我们使用微结构边界表面与 LC 弹性之间的耦合来引导大规模胶体结构的自组装。我们提出了胶体粒子在凸面突起（建模为与粒子大小相当的方形金字塔）存在下的自由能景观的显式数值计算。我们展示了存在能够有效定位胶体粒子并抵抗热波动的强捕获势。三维光学成像实验支持了理论预测。
