POWRE: Constrained Diffusion of an Isolated Colloidal Sphere in Confined Geometry

9870437 Lin该项目使用光镊结合数字视频显微镜来探测受限几何形状对孤立胶体球扩散的影响。该计划被分为两个不同的实验组的基础上的性质的限制的几何形状。在第一组实验中，将研究一个平面壁附近或两个平行平面壁之间的孤立球的扩散。光镊将被用来操纵的位置和扩散范围的球相对于墙壁。这些实验中的主要问题涉及中性或带电球体从中性或带电光滑玻璃壁或从“结构化壁”（如2D胶体晶体表面）的有效壁拖曳力。在第二组实验中，将研究被困在一维隧道或二维隧道网络中的球体的扩散。具有明确的空间结构的隧道或隧道网络将通过微接触印刷来制造。这些实验探测了球体的扩散与周围图案化受限几何形状的空间结构的相关性。所解决的问题是根本的利益，了解胶体流体力学。上述模型系统是代表与界面处或随机多孔结构中的大分子扩散相关的问题的限制性情况。实例包括运输过程，例如物理混合处理中的“单列扩散”、聚电解质在受限环境中的电扩散（测序大DNA分子中的电泳）、生长晶体前沿的液晶/晶体界面处的微泡扩散、细颗粒迁移和稳定乳液滴在多孔介质中的流动（与采油过程相关）。 这是根据研究和教育领域女性专业机会（POWRE）方案提供的研究增强补助金。这项研究将在基础层面上贡献新的材料科学知识。

9870437 Lin This project probes the effects of confined geometry on the diffusion of an isolated colloidal sphere using optical tweezers combined with digital video microscopy. The program is divided into two distinct groups of experiments based on the nature of the confined geometry. In the first group of experiments, the diffusion of an isolated sphere near one planar wall or confined between two parallel planar walls will be studied. Optical tweezers will be used to manipulate the position and the diffusion range of the sphere with respect to the walls. The main issue in these experiments involves the effective wall drag force on a neutral or charged sphere from a neutral or charged smooth glass wall or from a "structured wall" such as a 2D colloidal crystalline surface. In a second group of experiments, the diffusion of a sphere trapped in a one-dimensional tunnel or two-dimensional network of tunnels will be studied. The tunnels or tunnel-network with a well-defined spatial structure will be fabricated by microcontact printing. These experiments probe the correlation of the diffusion of a sphere to the spatial structure of the ambient patterned confined geometry. The issues being addressed are of fundamental interest for understanding colloidal hydrodynamics. The model systems noted above are limiting cases representing problems associated with diffusion of macromolecules either at interfaces or in random porous structures. Examples include transport processes such as "single file diffusion" in physical mixing processing, electrodiffusion of polyelectrolytes in confined environments (electrophoresis in sequencing large DNA molecues), microbubble diffusion at liquid/crystal interfaces of a growing crystal front, fine particle migration and flow of stable emulsion drops in porous media (relevant to oil recovery processes). %%% This is a research enhancement grant made under the Professional Opportunities for Women in Research and Education (POWRE) program. T he research will contribute new materials science knowledge at a fundamental level.