Directed Assembly by Capillarity

奖项：1066284 PI：StebeWe将进行基础研究，以建立各向异性毛细管组装的定量指导原则，即将颗粒形状，接触角和界面形状与相互作用的范围和强度以及形成的组装体联系起来。为此，我们将从实验、数值和理论三个方面对毛细管组装进行研究。我们已经建立了一个知识基础，以研究任何各向异性颗粒之间的相互作用，在接口，我们正在应用到圆柱形颗粒均匀的接触角的过程中。我们选择圆柱体作为研究的第一个形状，因为它们在界面处具有有趣的特性-它们在其平面端面附近具有高界面面积密度，这使得端对端组装。我们现在详细地了解了界面处圆柱形粒子之间的远场相互作用。然而，当颗粒靠近在一起时，末端附近的强烈变形重叠，形成颗粒之间的强烈相互作用，称为“毛细键”，其强度我们将用数值量化。 然后我们将通过实验来检验计算的有效性--这将建立所有分离处界面处圆柱体之间的相互作用对。然后，我们将解决三个组件的目标，选择铺平道路的领域，利用定向粒子组件。我们将：在实验中确定毛细管相互作用对于亚微米到纳米级颗粒是否重要，对于制造可退火结构和扩大毛细管组装的技术影响是否重要。二.使用磁性镊子表征毛细管组件的强度，这在利用颗粒稳定乳液、胶体体和其他分级组件的应用中非常重要。三.开发毛细管识别元件，它将优先组装只与交配粒子像拼图在接口上。这就要求我们开发和理解毛细管排斥，赋予选择性的颗粒相互作用。选择这些目标是为了播种新材料相关的研究，以利用各向异性颗粒组装体。例如，有序定向颗粒单层可以用来外延生长新的3-D结构;定向、组装的各向异性颗粒可以允许开发新类别的超材料;毛细识别元件可以促进颗粒与设备内其他特征的注册，并可以用作传感器或读出器。

Award: 1066284PI: StebeWe will perform fundamental studies to establish quantitative guiding principles for anisotropic capillary assembly, i.e. to relate particle shape, contact angle, and interface shape, to the range and strength of interactions and to the assemblies which form. To do so, we will study capillary assembly in experiment, numerics and theory. We have established an intellectual basis to study interactions between any anisotropic particles at interfaces which we are in the process of applying to cylindrically shaped particles with uniform contact angle. We choose cylinders as the first shape to study because they have intriguing properties when they are at interfaces- they have high interfacial area density near their planar end faces which cements end-to-end assembly. We now understand far field interactions between cylindrical particles at interfaces in detail. However, when the particles come close together, the strong deformations near the ends overlap, forming a strong interaction between particles termed a "capillary bond", whose strength we will quantify numerically. We will then check the validity of the calculation experimentally- this will establish the pair interactions between cylinders at interfaces at all separations. We will then address three assembly aims, selected to pave the way to fields which exploit oriented particle assemblies. We will: I. Establish in experiment whether, as scaling suggests, capillary interactions are important for sub-micron to nanoscale particles, important for making annealable structures and for extending the technological impact of capillary assembly. II. Characterize the strength of capillary assemblies using magnetic tweezers, important in applications that exploit particle-stabilized emulsions, colloidosomes, and other hierarchical assemblies. III. Develop capillary recognition elements, which would preferentially assemble only with mating particles like puzzle pieces on an interface. This requires that we develop and understand capillary repulsion to impart selectivity to particle interactions. These aims were selected to seed new materials-related research to exploit anisotropic particle assemblies. For example, ordered oriented particle monolayers could be exploited to epitaxially grow new 3-D structures; oriented, assembled anisotropic particles could allow new classes of metamaterials to be developed; capillary recognition elements could promote registry of particles with other features within devices, and could serve as sensors or read outs.