NER: 3D Nanocolloidal Crystallization via Electrokinetic Flows

我们最近开发了一种新颖和通用的方法，利用电场将胶体颗粒快速和可逆地排列成三维晶体。有序机制似乎依赖于诱导的偶极相互作用和流体动力流动的组合，这些流动将粒子推到一起，产生有效的吸引。由于这些相互作用可以通过外加场性质和限制几何的组合来调节，它们的大小可以被极大地调整，并用于结晶各种大小范围的粒子。我们的初步研究集中在半径从250 nm到50 nm的胶体，所有这些胶体都可以通过外加电场进行可逆结晶。我们还表明，这些胶体晶体的成核可以仅通过选择性地施加电场来进行空间控制。这里提出的工作的目标是将这些初步调查扩展到整个纳米范围内较小的长度范围。我们打算利用这一点来实现纳米粒子的可逆和空间可寻址结晶。除了创造一种廉价材料的显示技术外，我们还展望了基于纳米胶体材料的可逆有序的可切换光子带隙材料的发展。该奖项由化学和运输系统部门的热运输和热加工计划以及颗粒和多相工艺计划资助。

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.