CAREER: High-speed 3D Imaging of Colloidal Self-Assembly with Digital Holographic Microscopy

PI提出的研究的主要目标是研究胶体颗粒如何在受限和非平衡系统中自组装，包括被困在液-液界面（例如乳液液滴）和球形容器内的颗粒。尽管这些系统在工业配方和基本凝聚态物质研究中很常见，但人们对这些系统的了解仍然很少，主要是因为现有的实验探针，包括共聚焦显微镜，都不能以足够快的采集时间产生实时空间数据，以解决3D动力学问题。PI建议使用一种强大的干涉测量技术，数字全息显微镜（DHM），结合粒子合成和算法开发来克服这些限制。初步数据表明，该技术能够在毫秒时间尺度上以30纳米的空间精度在三个维度上跟踪几个微米大小的胶体颗粒。DHM可能能够提供迄今为止胶体悬浮液中动力学、相互作用和组装的最完整的物理图像。本研究旨在通过追求以下目标来回答胶体科学中的基本问题：用于研究胶体悬浮液的数字全息显微镜的开发和优化：该仪器的原型已经构建并显示了初步数据。PI将开发新的算法、数据采集技术和仪器，使该技术尽可能快速和健壮。2. 本仪器在以下实验研究中的使用：？测量被困在平面液-液界面的粒子的动力学：确定控制界面结合粒子组装的相互作用。？ 测量被困在球形液-液界面上的粒子的动力学和结构：研究被限制在乳液界面上的粒子的自组装结构。？ 界面内致密胶体的自组装成像：确定球形液滴边界对胶体晶体结构和组装的影响。本研究将为多相胶体体系的制定提供一个合理的框架，从而有利于工业产品的开发。它还将深入了解复杂流体中的结构形成，这可能对纳米制造有用。此外，一项综合教育和推广计划将针对剑桥学区的八年级理科学生，这是一个多元化的城市学校系统，大多数学生来自代表性不足的少数族裔和低收入家庭。该计划的目标是：1。开发一个设计模块，以吸引有风险的八年级理科学生：PI将与肯尼迪-朗费罗中学的一位老师密切合作，开发、实施和评估一个基于探究的学习计划，该计划(a)符合马萨诸塞州八年级物理和工程教学标准，(b)针对所有技能群体，包括特殊教育学生。来自新成立的工程与应用科学学院的哈佛大学本科生志愿者将被招募为导师和辅导员。更广泛的目标是通过指导、研究和开放式设计项目来教育和吸引更多的中学生。2. 研究型和导师型本科教育；研究生课程发展

0747625ManoharanThe primary goal of the PI's proposed research is to investigate how colloidal particles self-assemble in confined and nonequilibrium systems, including particles trapped at liquid-liquid interfaces (e.g. emulsion droplets) and inside spherical containers. Although common in industrial formulations and fundamental condensed matter studies, these systems remain poorly understood, primarily because no existing experimental probes, including confocal microscopy, can yield real-space data with sufficiently fast acquisition times to resolve 3D dynamics. The PI proposes to use a powerful interferometric technique, Digital Holographic Microscopy (DHM), in concert with particle synthesis and algorithm development to overcome these limitations. Preliminary data show that the technique is capable of tracking several micrometer-sized colloidal particles with 30 nm spatial precision in all three dimensions on millisecond time scales. DHM may be able to yield the most complete physical picture to date of dynamics, interactions, and assembly in colloidal suspensions. Intellectual MeritThe proposed research seeks to answer fundamental questions in colloid science by pursuing the following objectives: 1. Development and optimization of a Digital Holographic Microscope to investigate colloidal suspensions: A prototype of this instrument has been constructed and preliminary data are shown. The PI will develop new algorithms, data acquisition techniques, and instrumentation to make the technique as rapid and robust as possible. 2. Use of this instrument in the following experimental studies: ? Measuring the dynamics of particles trapped at planar liquid-liquid interfaces: determining the interactions governing the assembly of interfacially-bound particles. ? Measuring the dynamics and structure of particles trapped at spherical liquid-liquid interfaces: investigating the self-assembled structures of particles confined to an emulsion interface. ? Imaging self-assembly in dense colloids confined inside an interface: Determining the effect of a spherical droplet boundary on the structure and assembly of colloidal crystallites. Broader ImpactsThis work will benefit industrial product development by providing a rational framework for the formulation of multiphase colloidal systems. It will also yield insights into structure formation in complex fluids that may be useful in nanofabrication. In addition, an integrated education and outreach program will target 8th grade science students in the Cambridge school district, a diverse and urban school system with a majority of students from underrepresented minority groups and low-income households. Goals of the program are: 1. Developing a design module to engage at-risk 8th grade science students: The PI will work closely with a teacher from the Kennedy-Longfellow middle school to develop, implement, and assess an inquiry-based learning program that (a) meets Massachusetts standards for teaching physics and engineering in 8th grade and (b) targets all skill groups, including Special Education students. Harvard undergraduate volunteers from the new School of Engineering and Applied Sciences will be recruited as mentors and facilitators. The broader aim is to educate and engage more middle school students through mentorship, research, and open-ended design projects. 2. Undergraduate education through research and mentoring; graduate course development