NER: 3D Nanocolloidal Crystallization via Electrokinetic Flows

我们最近开发了一种新颖而通用的方法，利用电场将胶体粒子快速可逆地排列成三维晶体。排序机制似乎依赖于诱导偶极相互作用和流体动力流的结合，流体动力流将粒子推到一起，产生有效的吸引力。由于这些相互作用可以通过应用场性质和限制几何形状的组合来缓和，因此它们的大小可以大大调整，并用于在各种尺寸范围内结晶颗粒。我们的初步研究集中在粒径范围从250纳米到50纳米的胶体上，所有这些胶体都可以通过外场的应用可逆结晶。我们还表明，这些胶体晶体的成核可以通过选择性施加电场来控制。这里提出的工作目标是将这些初步研究扩展到整个纳米尺度范围内更小的长度尺度。我们打算利用这一点来实现纳米级颗粒的可逆和空间可寻址结晶。除了使用廉价材料创建显示技术外，我们还设想开发基于纳米胶体尺寸材料可逆顺序的可切换光子带隙材料。该合同由化学和运输系统分部的热传输和热处理项目以及颗粒和多相处理项目资助。

We have recently developed a novel and general means of ordering colloidal particles into three-dimensional crystals rapidly and reversibly using electric fields. The ordering mechanism appears to rely on a combination of induced dipole interactions and hydrodynamic flows that push particles together, creating an effective attraction. Because these interactions can be moderated with a combination of applied field properties and confining geometry, their magnitude can be greatly tuned and used to crystallize particles in a wide variety of size ranges. Our preliminary investigations have focused on colloids ranging in size from 250 nm down to 50 nm in radius, all of which can be reversibly crystallized through application of the external field. We have also shown that nucleation of these colloidal crystals can be spatially controlled solely through selective application of the electric field. The goal of the work proposed here is to extend these preliminary investigations into smaller length scales throughout the nanoscale range. We intend to take advantage of this for the reversible and spatially addressable crystallization of nanoscale particles. In addition to the creation of a display technology with inexpensive materials, we envision the development of switchable photonic band gap materials based upon the reversible ordering of nanocolloidal-sized materials. The award has been funded by the Thermal Transport and Thermal Processing Program and the Particulate and Multiphase Processes Program of the Chemical and Transport Systems Division.