Collaborative research: Using electric field and capillarity for particle self-assembly into adjustable monolayers

合作研究：利用电场和毛细管现象将颗粒自组装成可调节的单分子层

• 批准号: 1067272
• 负责人: Shawn Litster
• 金额: $ 18万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1067272&HistoricalAwards=false
• 关键词: Collaborative; research; Using; electric; field

Award: 1067272/1067004 PI: Aubry/SinghA novel technique in which an electric field is applied normal to an interface is being developed for self-assembling monolayers of particles with virtually defect-free ordering and desired/adjustable lattice spacing. Experiments and numerical simulations are used to develop models for the electrostatic forces that act on particles at an interface and thus for the lattice spacing. This capability will be useful to form materials with superior mechanical, electrical and optical properties, and has the potential to revolutionize many fields of science and technology, including optoelectronics and medicine. Capillarity-driven clustering of particles, the main mechanism used for self-assembly of neutral particle at fluid interfaces, has the following deficiencies: (i) the formed monolayer lacks order, (ii) it is restricted to particle radii greater than about 10 m; and (iii) the lattice is packed and not adjustable. All of these deficiencies are overcome by a novel technique in which an electric field is applied normal to the interface. The dipole-dipole repulsive force amongst particles together with the buoyant weight and the electrostatic force induced capillary forces, leads to the formation of virtually defect-free monolayers with adjustable spacing. Experiments and numerical simulations are conducted to determine the dependence of the vertical electrostatic forces on spherical and prismatic particles for a broad range of parameters and develop models for the capillary and lateral electrostatic forces, which determine the lattice spacing. Similar investigations will be conducted for other particles (ellipsoids, rods, etc.) to determine their stable relative orientations. Conditions will be determined under which the vertical electrostatic force pushes particles away from the interface. This is a phenomenon which should be prevented for the purpose of self-assembly, but is desired if one seeks to clean interfaces of trapped particles.Intellectual Merit. While close-packed self-assembly of particles is well-developed, the self-assembly into defect-free, homogeneous, adjustable, non-close-packed arrays of electrically neutral particles has remained a challenge. The present novel self-assembly technique is easy to implement and can be applied to a broad range of particle sizes and types with a high level of controllability, which will be useful in many applications including anti-reflection coatings for high efficiency solar and thermophotovoltaic (TPV) cells, photonic materials and biosensor arrays. Such applications require highly-ordered crystals with a non-zero, specific lattice gap which can be adjusted, e.g., according to the wavelength of the light or radiation going through the crystal. The work presents great intellectual challenges as it involves non-linear coupling between multiphase flows, interfacial fluid dynamics and electrostatics. Broader Impacts. The technique will have a great impact on our capability to (i) fabricate new microstructured surfaces with a desired pore size and (ii) dynamically alter the formed monolayers and interfacial properties in time, with numerous applications in micro/nanotechnology and colloidal science. The research will be fully integrated with education and outreach, with the involvement of graduate and undergraduate students, particularly women and underrepresented minorities, who will be involved in state-of-the-art research. Research results, in turn, will be incorporated into courses and outreach activities.

奖项：1067272/1067004 PI：Aubry/Singh 正在开发一种新技术，垂直于界面施加电场，用于自组装颗粒单层，具有几乎无缺陷的有序性和所需/可调节的晶格间距。实验和数值模拟用于开发作用于界面处粒子的静电力模型，从而开发晶格间距模型。这种能力将有助于形成具有优异机械、电学和光学性能的材料，并有可能彻底改变包括光电子和医学在内的许多科学技术领域。毛细管驱动的颗粒聚集是中性颗粒在流体界面自组装的主要机制，具有以下缺陷：（i）形成的单层缺乏有序性，（ii）它仅限于大于约 10 的颗粒半径和#61549；米； (iii) 网格是堆积的且不可调整。所有这些缺陷都可以通过一种新技术来克服，其中电场垂直于界面施加。颗粒之间的偶极-偶极排斥力以及浮力和静电力引起的毛细管力，导致形成具有可调节间距的几乎无缺陷的单层。进行实验和数值模拟以确定垂直静电力对球形和棱柱形颗粒的各种参数的依赖性，并开发用于确定晶格间距的毛细管和横向静电力的模型。将对其他粒子（椭球体、棒体等）进行类似的研究，以确定它们的稳定相对方向。将确定垂直静电力将颗粒推离界面的条件。这种现象应该为了自组装的目的而被防止，但如果人们试图清洁被捕获粒子的界面，则需要这种现象。智力优点。虽然颗粒的密堆积自组装技术已得到很好的发展，但自组装成无缺陷、均匀、可调节、非密堆积的电中性颗粒阵列仍然是一个挑战。目前的新型自组装技术易于实施，并且可应用于广泛的颗粒尺寸和类型，并且具有高水平的可控性，这将在许多应用中发挥作用，包括用于高效太阳能和热光伏的减反射涂层（ TPV）电池、光子材料和生物传感器阵列。此类应用需要具有非零、特定晶格间隙的高度有序晶体，该晶格间隙可以根据穿过晶体的光或辐射的波长进行调整。这项工作提出了巨大的智力挑战，因为它涉及多相流、界面流体动力学和静电学之间的非线性耦合。更广泛的影响。该技术将对我们的能力产生巨大影响：（i）制造具有所需孔径的新型微结构表面，以及（ii）及时动态改变形成的单分子层和界面特性，在微/纳米技术和胶体科学中具有广泛的应用。该研究将与教育和推广完全结合，研究生和本科生，特别是女性和代表性不足的少数族裔的参与，他们将参与最先进的研究。反过来，研究成果将被纳入课程和外展活动中。