Colloidal Micromechanics and Near-Contact Interactions

摘要-0500321特拉华大学我们建议研究的微观力学响应和近接触的相互作用，胶体凝胶的性质的基础。这将使用我们开发的基于光学捕获的新实验来实现，这使我们能够直接从单个胶体中组装模型聚集体，并在测量微观应力时可控地使其变形。拟议的工作将建立在探索性资助（NSF CTS-0209936）下获得的初步结果的基础上，在该研究中，我们展示并测量了近接触状态下胶体之间的切向相互作用。我们的工作首次量化了颗粒之间的单键弯曲刚度，并发现了聚集体的线性和非线性弯曲力学机制。这些性质依赖于物理化学条件，如溶液的离子强度和表面活性剂的吸附。要研究的力学，尚未认识到，到现在为止，有相当大的后果颗粒凝胶的加工和性能，因为它们的屈服应力，老化性能和这些材料的模量的影响。 这里提出的活动将建立在两年探索性资助的成功基础上，并将大大扩展这一活动，以根据我们获得的见解开发新的实验。此外，我们将与来自其他大学的研究小组合作，他们将通过AFM带来建模异质胶体相互作用和颗粒表征的专业知识。 我们期待这项工作将产生重大的技术影响，因此我们已将自己定位为杜邦汽车涂料事业部内富有成效的行业合作和联系人。由于颗粒凝胶出现在各种各样的制造过程中，包括涂料，药物制剂，陶瓷部件制造，矿物回收和润滑剂降解，因此预测和控制其性能的能力受到相当大的关注。甘氨酰也对蛋白质结晶产生不利影响，限制了蛋白质结构和功能的表征。虽然近年来已经有了显着的进展，颗粒凝胶的机械和流变性能的基础上，颗粒间的相互作用，微观结构和微观力学的基本机制还没有得到充分的理解。 通过跨越纳米和微米尺度物理到宏观行为，我们将建立合成新材料所需的基本原理，并改进现有材料中产品和加工性能的预测和控制。此外，对胶体相互作用的理解和控制是这项工作的一个自然方面，超越了凝胶流变学，扩展到新的和新兴的应用，如光子晶体，化学生物传感器和纳米技术。 缺乏能够检查非理想胶体表面之间的近接触相互作用的实验方法被认为是一个急需发展的领域，我们有充分的能力来解决这个问题。这项工作将为两名研究生提供胶体科学技术关键领域的教育和研究培训。通过我们与耶鲁大学和杜邦马歇尔实验室的交流，这种培训经验将得到显著增强。资金将支持一名本科研究生完成荣誉论文。迄今为止，这项工作已经产生了重大的教育影响，产生了一个MChE（目前是一个入学博士）。学生），三个本科生荣誉论文（两篇论文的合著者在准备），目前，一个高年级论文的学生，谁预计将合著两篇即将发表的论文。这项研究的结果将通过在期刊上发表文章和在国家和国际科学会议上发表演讲，广泛传播给科学家和工程师。

ABSTRACT - 0500321University of DelawareWe propose to investigate the micromechanical response and near-contact interactions that underlie the properties of colloidal gels. This will be accomplished using novel experiments we have developed based on optical trapping, which enables us to directly assemble model aggregates from individual colloids and controllably deform them while measuring microscopic stresses. The proposed work will build on the preliminary results obtained under an exploratory grant (NSF CTS-0209936), in which we demonstrated and measured tangential interactions between colloids that arise in near-contact regimes. Our work quantified, for the first time, the single-bond bending rigidity between particles, and discovered regimes of linear and non-linear bending mechanics of aggregates. These properties have dependences on physico-chemical conditions, such as the solution ionic strength and adsorption of surfactants. The mechanics to be studied, unrecognized until now, have considerable consequences for the processing and properties of particulate gels, because of their influence on the yield stress, aging properties and moduli of these materials. The activity proposed here will build upon the successes of two years of exploratory funding, and will significantly extend this activity to develop new experiments based on insights we have gained. In addition, we will work with research groups from other universities who will bring expertise in modeling heterogeneous colloidal interactions and particle characterization via AFM. Expecting that this work will have a significant technological impacts, we have positioned ourselves for productive industrial collaborations and contacts within the DuPont Automotive Coatings Division.Intellectual Merit. Because particulate gels occur in a wide variety of manufacturing processes, including coatings, pharmaceutical formulations, ceramic parts manufacturing, mineral recovery and lubricant degradation, there is considerable interest in the ability to predict and control their properties. Gelation also adversely affects efforts to crystallize proteins, limiting the characterization of protein structure and function. Although there have been notable advances in recent years, the fundamental mechanisms of the mechanical and rheological properties of particulate gels based on interparticle interactions, microstructure and micromechanics have yet to be fully understood. By spanning the nano- and micro-scale physics to macroscopic behavior, we will establish the fundamentals needed to synthesize new materials, and improve the prediction and control of product and processing properties in existing materials. Furthermore, the understanding and control of colloidal interactions that are a natural aspect of this work, extends beyond gel rheology to novel and emerging applications, such as photonic crystals, chembiosensors and nanotechnology. The lack of experimental methods capable of examining near-contact interactions between nonideal colloidal surfaces has been cited as an area in critical need of development, which we are well-equipped to address.Broader Impacts. This work will provide education and research training for two graduate students in the technologically-critical field of colloid science. This training experience will be significantly enhanced through our interactions with groups at Yale Unviersity and DuPont Marshall Labortory. Funds will support one undergraduate research student to complete an Honors thesis. To date, this work has had a significant educational impact, resulting in one MChE (currently a matriculated Ph.D. student), three undergraduate honors theses (co-authors on two papers in preparation) and, currently, one senior thesis student, who is expected to co-author two upcoming papers. Results of this research will reach a broad community of scientists and engineers through publications in journals and presentations at national and international scientific meetings.