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: 1067004
• 负责人: Pushpendra Singh
• 金额: $ 18万
• 依托单位: New Jersey Institute of Technology
• 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 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1067004&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：1067277 /1067004奖：Aubry/ singa一种新技术，该技术将电场法向界面施加，用于自组装单层粒子，具有几乎无缺陷的有序和期望/可调的晶格间距。实验和数值模拟用于建立作用于界面上粒子的静电力模型，从而用于晶格间距。这种能力将有助于形成具有优异机械、电气和光学性能的材料，并有可能彻底改变许多科学和技术领域，包括光电子学和医学。毛细管驱动的粒子聚集是中性粒子在流体界面上自组装的主要机制，它有以下缺陷：(i)形成的单层缺乏秩序；（ii）它仅限于粒子半径大于10 &amp；#61549;m；（三）晶格是填充的，不可调节。所有这些缺陷都被一种新技术所克服，在这种新技术中，电场向界面施加法向。粒子之间的偶极-偶极斥力，加上浮力和静电力引起的毛细力，导致形成几乎没有缺陷的单层，具有可调节的间距。通过实验和数值模拟来确定垂直静电力对球形和棱柱形粒子的依赖关系，并建立了毛细管静电力和横向静电力的模型，这些静电力决定了晶格间距。对其他粒子（椭球、棒状等）也将进行类似的研究，以确定它们的稳定相对方向。将确定在何种条件下，垂直静电力将粒子推离界面。这是一种应该防止自组装的现象，但如果试图清洁被捕获粒子的界面，则需要这种现象。知识价值。虽然紧密排列的粒子自组装已经发展得很好，但自组装成无缺陷、均匀、可调节、非紧密排列的电中性粒子阵列仍然是一个挑战。这种新型的自组装技术易于实现，可以应用于广泛的粒径和类型，具有高度的可控性，这将在许多应用中有用，包括高效太阳能和热光伏（TPV）电池的抗反射涂层，光子材料和生物传感器阵列。这种应用需要高度有序的晶体，具有非零的特定晶格间隙，可以调整，例如，根据穿过晶体的光或辐射的波长。由于涉及到多相流之间的非线性耦合、界面流体动力学和静电学，这项工作提出了巨大的智力挑战。更广泛的影响。该技术将对我们的能力产生重大影响：(1)制造具有理想孔径的新微结构表面；(2)及时动态改变形成的单层和界面特性，并在微/纳米技术和胶体科学中得到广泛应用。这项研究将与教育和外联活动充分结合起来，研究生和本科生，特别是妇女和代表性不足的少数民族的学生将参与最新的研究。研究结果又将纳入课程和外联活动。