GOALI: The Effects of Heterogeneities on Surface Forces and Colloidal Stability

摘要CTS-0350630J。耶鲁大学沃尔茨-这项目标提案将是耶鲁大学研究人员和NExpress Solutions LLC之间的合作努力，旨在开发改进的模型，用于预测异质性对颗粒和表面之间的长程和粘附力的影响。NExpress是柯达和Heidelberger Druckmaschinen AG的合资企业，开发和生产数字印刷设备。了解表面粗糙度或表面电荷不均匀形式的异质性的影响，在任何与颗粒沉积或粘附性或颗粒分散体的稳定性有关的过程中都是重要的。这在电子照相过程中尤其关键，在电子照相过程中，碳粉颗粒既粗糙又不均匀带电，必须通过施加的电场从它们附着的导电衬底转移到接收表面。虽然不同的研究人员已经解决了表面粗糙度或电荷不均匀的具体问题，但这项工作将是第一个以严格的方式包括这两种影响的工作。该项目的智力价值该项目将包括建模和实验两部分。首先，将建立一个模型来计算平面衬底与任意粗糙度和电荷分布的粒子之间的静电力和范德华力。这项工作将建立在其中一个PI的先前工作的基础上，其中开发了一个边界元模型来计算任意形状的两个带电粒子之间的静电相互作用。此外，还将计算分离附着颗粒所需的电场强度，这是电子照相过程中的一个关键参数。这些模型在空气和水环境中都有效。这项旨在验证模型预测的实验工作将包括使用原子力显微镜(单个粒子测量)和离心力分离(多个粒子的分离)等技术直接测量粘附力和力与距离的分布。通过控制纳米颗粒的沉积，颗粒上的粗糙程度将有所不同。该项目还将解决非均质性对颗粒分散体稳定性的影响。这项工作将有四个主要成果：(1)将建立一个严格的边界元模型，能够预测具有表面粗糙度和电荷不均匀的颗粒与衬底之间的静电力和范德华力，(2)将建立一个改进的近似模型，用于计算粗糙度可控的粗糙度颗粒与平面衬底之间的粘附力，(3)将测试一种产生粗糙度可控的颗粒的简单方法，以及(4)将彻底分析表面粗糙度和电荷不均匀对胶体分散体稳定性的影响。这些结果将大大提高我们预测和控制颗粒沉积和粘连的能力，以及胶体分散体的稳定性。该项目的更广泛影响该项目将促进耶鲁大学和NExpress之间的合作关系。它将为博士后研究和博士后研究生提供直接支持。此外，这名研究生将在纽约罗切斯特的NExpress实验室工作长达一年，以获得工业研究环境的经验。最后，该项目将为耶鲁大学化学工程系目前提供的一系列胶体和复杂流体课程提供新的材料，这将加强我们在这些领域的研究生课程。

AbstractCTS-0350630J. Walz, Yale UniversityThis GOALI proposal will be a collaborative effort between researchers at Yale University and NexPress Solutions LLC aimed at developing improved models for predicting the effect of heterogeneities on both the long-range and adhesive forces between particles and surfaces. NexPress is a joint venture between Kodak and Heidelberger Druckmaschinen AG that develops and produces digital printing equipment. Understanding the effects of heterogeneities, in the form of either surface roughness or surface charge heterogeneity, is important in any process concerned with the deposition or adhesion of particles, or the stability of a particle dispersion. It is especially critical in the electrophotographic process, where toner particles, which are both rough and nonuniformly charged, must be transferred via an applied electric field from a conductive substrate, to which they are adhered, to the receiving surface. While various researchers have addressed the specific problems of either surface roughness or charge nonuniformity, this work will be the first that includes both effects in a rigorous manner. Intellectual Merit of the Project This project will consist of both modeling and experimental components. First, a model will be developed for calculating the electrostatic and van der Waals forces between a planar substrate and a particle of arbitrary roughness and charge distribution. This work will build upon prior work by one of the PI's in which a boundary element model was developed for calculating the electrostatic interaction between two charged particles of arbitrary morphology. In addition, the electric field strength needed to detach an adhered particle, which is a critical parameter in the electrophotographic process, will be calculated. The models will be valid in both air and aqueous environments. The experimental work, which will be designed to validate the model predictions, will consist of direct measurements of both the adhesion force and the force-vs-distance profile using techniques such as atomic force microscopy (single particle measurements) and centrifugal detachment (detachment of many particles). The degree of roughness on the particles will be varied using controlled deposition of nanoparticles. The project will also address the effects of heterogeneities on the stability of a particle dispersion. There will be four primary outcomes of this work: (1) a rigorous boundary element model capable of predicting the electrostatic and van der Waals forces between a substrate and particle having both surface roughness and charge heterogeneity will be developed, (2) an improved, approximate model for calculating the adhesion force between a rough, elastic particle and planar substrate will be developed, (3) a simple method for producing particles with controlled degrees of roughness will be tested, and (4) a thorough analysis of the effect of both surface roughness and charge heterogeneity on the stability of a colloidal dispersion will be performed. These outcomes will significantly advance our ability to predict and control the deposition and adhesion of particles, as well as the stability of a colloidal dispersion. Broader Impacts of the Project This project will promote a collaborative relationship between Yale and NexPress. It will provide direct support for a post-doctoral research and Ph.D. graduate student. In addition, the graduate student will spend up to one year at NexPress laboratories in Rochester, NY, gaining experience with an industrial research environment. Finally, the project will contribute new material to a series of courses in colloids and complex fluids that are currently offered in Yale's chemical engineering department, which will enhance our graduate program in these areas.