Curvature gradient driven assembly of trapped and reconfigurable structures

俘获和可重构结构的曲率梯度驱动组件

• 批准号: 1607878
• 负责人: Kathleen Stebe
• 金额: $ 42.75万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607878&HistoricalAwards=false
• 关键词: Curvature; gradient; driven; assembly; trapped

Non-technical AbstratThe ability to organize microscale particles into well-defined structures lies at the heart of our ability to design new soft, reconfigurable materials. Often, external electrostatic or magnetic fields are used to guide particles into positions where they can interact and form structures. This work studies fields that have not been widely appreciated or used in the past. Particles on fluid interfaces deform and increase the area of the interface around them. The product of surface tension and this area increase is an energy field that depends on the curvature of the fluid interface, so particles move along curvature gradients. Through this simple but remarkable fact, the geometry of the interface itself can be used to direct assembly. Here, these fields are studied to identify new ways to form structures difficult to form by conventional means to make new materials whose properties are explored. Graduate and undergraduate students are trained in the course of performing the proposed research, including students in the Louis Stokes Alliance for Minority Participation program, the Advancing Women in Engineering Program and the UPENN MRSEC REU program. New knowledge developed will be incorporated in a graduate course on interfacial phenomena.Technical AbstractThis research seeks to establish new strategies for directed assembly of micron and sub-micron scale particles to go well beyond the usual close packed assemblies. Particle trapped at fluid interfaces interact and migrate along interface curvature gradients via capillarity. These energies drive formation of complex structures strongly correlated with the interface curvature field, influenced by particle-particle interactions. Since soft matter is inherently deformable, such interactions are a natural route to form reconfigurable, tunable assemblies. Different classes of structures are studied using optical microscopy to observe structures, lithographically defined vessels to mold fluid interfaces and magnetic and other probes to perturb the structures and to guide their reconfiguration. Kinetically trapped structures are studied to form colloidal monolayer membranes with voids, dense regions and oriented structures which respond to changes in interface shape. Equilibrated structures are studied to form structures aligned along principle axes of the interfaces and to study their reconfiguration upon interface perturbation. The (dynamics of) structure formation is observed by optical microscopy for particle shapes and sizes selected for the scale of capillary interactions that they excite and their ability to form oriented structures with associated anisotropies in the structural response to perturbation. For both limits, particle positions/ orientations are compared to and correlated with the interface curvature. Observations are compared to appropriate prediction based on, for example, Stokesian Dynamics simulations for trapped structures and Monte Carlo simulations for equilibrated structures.

非技术摘要将微米级颗粒组织成明确结构的能力是我们设计新型柔软、可重构材料能力的核心。 通常，外部静电或磁场用于引导粒子进入可以相互作用并形成结构的位置。这项工作研究了过去没有被广泛重视或使用的领域。 流体界面上的颗粒会变形并增加它们周围的界面面积。表面张力和面积增加的乘积是一个能量场，该能量场取决于流体界面的曲率，因此粒子沿着曲率梯度移动。 通过这个简单但值得注意的事实，界面本身的几何形状可以用来指导组装。 在这里，对这些领域进行研究，以确定形成传统方法难以形成的结构的新方法，从而制造其特性得到探索的新材料。研究生和本科生在进行拟议研究的过程中接受了培训，包括路易斯·斯托克斯少数族裔参与联盟项目、推进女性工程项目和 UPENN MRSEC REU 项目的学生。开发的新知识将纳入界面现象研究生课程中。技术摘要本研究旨在建立微米和亚微米级颗粒定向组装的新策略，以远远超出通常的密堆积组装。 捕获在流体界面处的颗粒通过毛细作用沿着界面曲率梯度相互作用和迁移。 这些能量驱动与界面曲率场密切相关的复杂结构的形成，并受到粒子-粒子相互作用的影响。由于软物质本质上是可变形的，因此这种相互作用是形成可重构、可调组件的自然途径。研究不同类别的结构，使用光学显微镜观察结构，使用光刻定义的容器来塑造流体界面，并使用磁性和其他探针来扰动结构并指导其重新配置。研究动力学捕获结构以形成具有空隙、致密区域和响应界面形状变化的定向结构的胶体单层膜。研究平衡结构以形成沿界面主轴对齐的结构，并研究它们在界面扰动时的重新配置。 通过光学显微镜观察结构形成（的动力学），选择颗粒形状和尺寸，这些形状和尺寸是根据它们激发的毛细管相互作用的规模以及它们在结构对扰动的响应中形成具有相关各向异性的定向结构的能力而选择的。对于这两个限制，粒子位置/方向与界面曲率进行比较并相关。 将观察结果与基于例如捕获结构的斯托克斯动力学模拟和平衡结构的蒙特卡罗模拟的适当预测进行比较。