Microdynamics and Macroscopic Function of Active Colloidal Gels

CBET-1702418PI：所罗门，迈克尔当胶体颗粒的浓缩悬浮液形成颗粒网络时，结果是一种被称为软胶体凝胶的材料。胶体凝胶的弹性性能可以通过改变颗粒的特性来调节，这使得胶体凝胶在许多消费品、农业应用和制药中都有应用。该奖项将支持将活性颗粒融入其结构的胶体凝胶的开发和表征。活性粒子在一定条件下可以产生自身的推进力。将活性粒子嵌入到胶体凝胶中，可以扩大胶体凝胶性质变化和控制的程度，从而增加胶体凝胶在实际中的应用。含有活性颗粒的凝胶的性能将使用显微镜和机械测试相结合的方法进行研究。研究结果将通过行业/学术研讨会传播。此外，这项研究还将被用来为参加暑期学校的中学女孩创建动手演示，该学校向年轻学生介绍工程学。本项目将建立胶体凝胶中活性胶体的微观动力学与其线弹性和非线性屈服的宏观功能特性之间的关系。这些微观/宏观关系将通过研究引入到分形团簇凝胶中的活性胶体来产生，该体系的结构、动力学、弹性和屈服对于被动的布朗胶体来说是很好的理解的。由过氧化氢分解驱动的活性铂Janus颗粒、双通道共聚焦显微镜、分形簇凝胶自组装以及带有新型渗透夹具的宏观流变学将被用于发现：(I)微观活动如何影响凝胶的线弹性模数；(Ii)内部诱导屈服如何在宏观上呈现；以及(Iii)凝胶的固结和崩解是如何由活性胶体的外部压力产生的。这项工作将深入了解活性体系的不同寻常的微观动力学如何决定其宏观流变功能。

CBET - 1702418PI: Solomon, MichaelWhen a concentrated suspension of colloidal particles forms networks of particles, the result is a material called a soft colloidal gel. The elastic properties of colloidal gels can be tuned by changing the characteristics of the particles, which makes colloidal gels useful in many consumer products, agricultural applications, and pharmaceuticals. This award will support the development and characterization of colloidal gels that incorporate active particles into their structures. Active particles can generate their own propulsion under certain conditions. When active particles are embedded in a colloidal gel, the extent to which the properties of the gel can be varied and controlled is expanded, which could increase the use of colloidal gels in practice. The properties of the gels containing active particles will be investigated using a combination of microscopy and mechanical testing. Results of the research will be disseminated through an industry/academic workshop. In addition, the research will be used to create hands-on demonstrations for middle school girls participating in a summer school that introduces young students to engineering. This project will establish the relationship between the microdynamics of active colloids embedded in colloidal gels and their macroscopic functional properties of linear elasticity and non-linear yielding. These micro/macro relationships will be generated by investigating active colloids introduced into fractal cluster gels, a system whose structure, dynamics, elasticity, and yielding are well understood for the case of passive, Brownian colloids. Active platinum Janus particles driven by hydrogen peroxide decomposition, two-channel confocal microscopy, fractal cluster gel self-assembly, and macroscopic rheology with a novel, permeable fixture will be used to discover: (i) how microscopic activity affects the linear elastic modulus of gels; (ii) how internally-induced yielding presents macroscopically, and; (iii) how consolidation and disintegration of gels is produced by the external pressure of active colloids. The work will yield insight into how the unusual microdynamics of active systems determine their macroscopic rheological function.