EAGER: A New Class of Self-Assembled Photorheological Fluids

EAGER：一类新型自组装光流变液体

• 批准号: 1062123
• 负责人: Srinivasa Raghavan
• 金额: $ 6.83万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1062123&HistoricalAwards=false
• 关键词: EAGER; New; Class; Self; Assembled

1062123RaghavanPhoto-rheological (PR) fluids are those whose rheological or flow properties such as their viscosity can be dramatically altered by illumination with light. Previous formulations of such fluids have necessitated the use of sophisticated organic molecules such as photo-responsive surfactants or polymers. However, the difficulty and cost involved in synthesizing these complex molecules has hampered research in this field. There is a need for low-cost PR fluids that can be prepared using only simple, commercially available nano-scale amphiphilic molecules. If such fluids were available, it is likely to have a transformative effect on a variety of scientific and engineering disciplines. Building on a successful CAREER project, the PI proposes to explore a new class of photo-reversible PR fluids that can be reversibly transformed from low to high viscosity by irradiation with different wavelengths of light. Most importantly, the proposed fluids will only use two commercially available molecules: a cationic surfactant and an azobenzene derivative. The results of this EAGER project are likely to represent a conceptual breakthrough in the field of stimuli-responsive fluids. The preliminary data will provide a framework for a larger systematic study on photo-reversible PR fluids, both aqueous and non-aqueous. Intellectual Merit: The proposed aqueous PR fluids are expected to be based on self-assembled nano-structures called "wormlike micelles", the properties of which will be impacted by the extent of binding of the azobenzene photoisomer. Irradiation with one wavelength of light is expected to elongate these micelles and thereby produce an increase in fluid viscosity. Conversely, irradiation at a different wavelength of light is expected to shorten the micelles and thereby induce a drop in the fluid viscosity. The PI hypothesizes that deviations from planarity of the photoisomer dictate its binding efficacy. This proposal will explore the rheological response of the PR fluids in steady and dynamic (oscillatory) shear before, during, and after irradiation with light at different wavelengths. The results will be correlated with microstructural studies using small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). Altogether, the study is expected to yield a coherent scientific picture for the behavior of these novel fluids. Broader Impact: Compared to other stimuli-responsive systems, PR fluids represent a fresh and exciting technology. This project will help to bring PR fluids "into the mainstream" by offering a range of simple, reversible systems that can be prepared in any laboratory using low-cost commercially available molecules. Potential applications for PR fluids include microfluidic valves, microscale robots, and drag-reducing fluids; additional applications are likely to arise once more scientists begin to explore these systems. Also, fundamental insight on light-responsive self-assembly from this work could be extended to structures other than micelles. This project will also support the graduate training and education of a student in the PI's department at University of Maryland.

1062123 Raghavan光流变液(PR)是指其流变性或流动特性(如粘度)可通过光照显著改变的流体。以前的这类流体配方需要使用复杂的有机分子，如光响应性表面活性剂或聚合物。然而，合成这些复杂分子的难度和成本阻碍了这一领域的研究。需要低成本的PR液，这种油只能使用简单的、商业上可获得的两亲纳米分子来制备。如果有这样的流体，它很可能会对各种科学和工程学科产生革命性的影响。在一个成功的职业项目的基础上，PI建议探索一种新型的可光可逆PR液体，这种液体可以通过不同波长的光照射从低粘度可逆转变为高粘度。最重要的是，拟议的流体将只使用两个商业上可用的分子：阳离子表面活性剂和偶氮苯衍生物。这个急切的项目的结果很可能代表着刺激响应液领域的概念突破。初步数据将为对水和非水的光可逆PR流体进行更大规模的系统研究提供一个框架。智能优点：拟议的水性PR液预计将基于被称为“蠕虫状胶束”的自组装纳米结构，其性质将受到偶氮苯光异构体结合程度的影响。用一个波长的光照射有望拉长这些胶束，从而增加流体粘度。相反，在不同波长的光照射预计会缩短胶束，从而导致流体粘度下降。等电点假设，偏离光异构体的平面度决定了它的结合效率。该方案将探索PR流体在不同波长的光照射之前、期间和之后在稳态和动态(振荡)剪切中的流变性响应。这些结果将与使用小角中子散射(SANS)和低温透射电子显微镜(Cryo-TEM)进行的微观结构研究相关联。总之，这项研究有望为这些新型流体的行为提供一幅连贯的科学图景。更广泛的影响：与其他刺激反应系统相比，PR液代表着一种新鲜而令人兴奋的技术。该项目将通过提供一系列简单、可逆的系统，帮助将PR液“带入主流”，这些系统可以在任何实验室使用低成本的商业可获得分子来制备。PR流体的潜在应用包括微流体阀、微型机器人和减阻流体；当更多的科学家开始探索这些系统时，可能会出现更多的应用。此外，这项工作对光响应性自组装的基本见解可以扩展到胶束以外的结构。该项目还将支持马里兰大学PI系的一名学生的研究生培训和教育。