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

9870437在这个项目中，使用光学镊子和数字视频显微镜相结合的方法来探索受限几何形状对孤立胶体球体扩散的影响。该程序根据受限几何的性质分为两组不同的实验。在第一组实验中，将研究孤立球在一个平面壁附近的扩散或限制在两个平行平面壁之间的扩散。光学镊子将被用来操纵球体相对于墙壁的位置和扩散范围。这些实验中的主要问题涉及从中性或带电的光滑玻璃墙或来自诸如2D胶体晶体表面的“结构墙”对中性或带电球体的有效壁阻力。在第二组实验中，将研究困在一维隧道或二维隧道网络中的球体的扩散。具有明确空间结构的隧道或隧道网络将通过微接触打印来制造。这些实验探索了球体的扩散与周围有图案的受限几何图形的空间结构的相关性。正在解决的问题对理解胶体流体动力学具有根本意义。上面提到的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极限情况。例如，物理混合过程中的“单列扩散”、受限环境中聚电解质的电扩散(DNA大分子测序中的电泳法)、不断生长的晶体前沿液/晶界面上的微气泡扩散、细小颗粒的迁移以及稳定的乳状液滴在多孔介质中的流动(与采油过程有关)。%这是根据妇女在研究和教育中的职业机会(POWRE)计划提供的研究增强补助金。这项研究将在基础水平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.