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.

奖励：1067272/1067004 PI：Aubry/Singha小说技术，其中将电场态度归一部分为界面，以用于自组装单层的粒子单层，这些单层实际上是无缺陷的订购和可调的/可调节的晶格间距。实验和数值模拟用于开发用于在界面和晶格间距上作用于颗粒的静电力的模型。该能力将有助于形成具有出色的机械，电气和光学特性的材料，并有可能彻底改变科学和技术的许多领域，包括光电和医学。粒子的毛细血管驱动的聚类是流体界面上中性粒子自组装的主要机制，具有以下缺陷：（i）形成的单层缺乏顺序，（ii）它仅限于粒子半径大于大约10＆＃61549; m; m; （iii）晶格已包装，不可调节。所有这些缺陷都通过一种新技术来克服，在这种新技术中，将电场应用于界面。颗粒之间的偶极 - 偶极反击力与浮力和静电力诱导的毛细作用力，导致形成具有可调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广泛参数的球形和棱镜颗粒的依赖性，并为确定晶格间距的毛细管和侧静电力开发模型。将针对其他颗粒（椭圆形，杆等）进行类似的研究，以确定其稳定的相对取向。将确定垂直静电力将颗粒从界面推开的条件。这是一种现象，应出于自组装的目的而预防，但是如果有人试图清洁被困颗粒的界面，则需要。虽然颗粒的紧密包装的自组装已经充分发达，但自组装成无缺陷，均匀，可调，不闭合的电气中性颗粒阵列仍然是一个挑战。当前的新型自组装技术易于实现，可以应用于具有高可控性的各种颗粒大小和类型，这将在许多应用中有用，包括用于高效太阳能和热伏型（T​​PV）细胞（TPV）细胞的抗反射涂层，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排序的晶体，例如，根据穿过晶体的光或辐射的波长，可以调整该晶体。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之间的非线性耦合。更广泛的影响。该技术将对我们（i）制造具有所需孔径的新微观结构表面的能力产生很大的影响，并且（ii）在时间上动态更改形成的单层和界面特性，并在微/纳米技术和胶体科学中进行许多应用。这项研究将与教育和外展充分融合，研究生和本科生，尤其是妇女和代表性不足的少数群体，他们将参与最新的研究。反过来，研究结果将纳入课程和外展活动中。