Decoupling dynamics from the rheology of surface-anisotropic colloids

从表面各向异性胶体流变学中解耦动力学

• 批准号: 1804462
• 负责人: Lilian Hsiao
• 金额: $ 30万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1804462&HistoricalAwards=false
• 关键词: Decoupling; dynamics; rheology; surface; anisotropic

Colloids consist of micron-sized particles dispersed in a fluid. Due to the small size of the particles, their motion is affected by collisions with the fluid molecules. Colloids are found in a broad range of engineered products, such as pharmaceuticals, dairy foods, and oil slurries. Despite their ubiquity, traditional engineering approaches have not accounted for the fact that these particles possess rough surfaces. This difference in shape from a perfect, idealized, smooth sphere does not cause problems when the particle loading is low. However, when such particles are packed more closely, large disagreements between experimental data and theories are found. These deviations have hampered the engineering of processing flow conditions for suspensions containing rough particles that generate frictional interactions due to solid-solid contact. The goal of this project is to investigate the effect of colloidal surface roughness on a variety of flow phenomena. Connections between dynamics, microstructure, and properties of the suspensions will be made using a specially constructed apparatus mounted on a confocal microscope. The results from this work will lead to design rules for industry for the use of colloid particles with rough or irregular surfaces in their products. In addition, knowledge gained from this project will be used in outreach activities that utilize social media for STEM education. A series of Reddit interactive outreach activities that present complex scientific concepts about the flow and texture of materials in an interesting and digestible way will be made available to the general public. The goal is to capture the imagination of the nation's younger generation and to guide them towards the wonders and discoveries present in today's science and engineering careers.This award aims to understand the microscopic dynamics of model polymeric colloids with well-controlled surface anisotropy. The central hypothesis is that the translational and rotational diffusion of colloids with various surface features becomes independently decoupled at high particle loadings. The decoupling of dynamics leads to significant departures in the linear and nonlinear rheology from current theoretical predictions. This work will generate new physical understanding of how particle diffusivity affects the linear and nonlinear rheology of concentrated suspensions. In this regime, fluid suspensions become increasingly glassy in their mechanical properties. The fundamental rationale behind these phenomena is still not well understood, particularly when particles make solid-solid contacts with one another. This work will investigate the microscopic mechanisms by imaging smooth and rough colloids flowing within a fast confocal rheometer setup designed to concurrently capture rotational dynamics during shear flow. Brownian Dynamics simulations with short-range hydrodynamic interactions will be incorporated to support experimental observations of dynamics and connections to glassy rheology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

胶体由分散在流体中的微米级颗粒组成。 由于颗粒的尺寸很小，它们的运动受到与流体分子碰撞的影响。胶体存在于广泛的工程产品中，如药品、乳制品和油浆。尽管它们无处不在，但传统的工程方法并没有考虑到这些颗粒具有粗糙表面的事实。当颗粒负载较低时，这种与完美、理想化、光滑球体的形状差异不会引起问题。然而，当这些颗粒堆积得更紧密时，发现实验数据和理论之间存在很大的差异。这些偏差阻碍了含有粗糙颗粒的悬浮液的加工流动条件的工程设计，这些颗粒由于固-固接触而产生摩擦相互作用。这个项目的目标是研究胶体表面粗糙度对各种流动现象的影响。动力学，微观结构和性能之间的连接的悬浮液将使用一个专门构造的装置安装在共聚焦显微镜。 这项工作的结果将导致工业设计规则，用于在其产品中使用具有粗糙或不规则表面的胶体颗粒。此外，从该项目中获得的知识将用于利用社交媒体进行STEM教育的外联活动。一系列Reddit互动推广活动将以有趣和易于理解的方式向公众介绍有关材料流动和质地的复杂科学概念。该奖项旨在激发年轻一代的想象力，并引导他们探索当今科学和工程事业中的奇迹和发现。该奖项旨在了解具有良好控制的表面各向异性的模型聚合物胶体的微观动力学。中心假设是，具有各种表面特征的胶体的平移和旋转扩散在高颗粒负载下变得独立解耦。动力学的解耦导致显着偏离的线性和非线性流变学从目前的理论预测。这项工作将产生新的物理理解如何颗粒扩散影响的线性和非线性流变浓悬浮液。在这种情况下，流体悬浮液的机械性能变得越来越玻璃化。这些现象背后的基本原理仍然没有得到很好的理解，特别是当颗粒彼此进行固-固接触时。这项工作将调查的微观机制，通过成像光滑和粗糙的胶体流动在一个快速的共焦流变仪设置，旨在同时捕捉剪切流动过程中的旋转动力学。布朗动力学模拟与短程流体动力学相互作用将被纳入，以支持实验观察的动态和连接到玻璃流变学。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

项目成果

Contact criterion for suspensions of smooth and rough colloids

光滑和粗糙胶体悬浮液的接触准则

• DOI: 10.1039/d0sm00072h
• 发表时间: 2020
• 期刊: Soft Matter
• 影响因子: 3.4
• 作者: Pradeep, Shravan;Hsiao, Lilian C.
• 通讯作者: Hsiao, Lilian C.

Jamming Distance Dictates Colloidal Shear Thickening

干扰距离决定胶体剪切增稠

• DOI: 10.1103/physrevlett.127.158002
• 发表时间: 2021
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Pradeep, Shravan;Nabizadeh, Mohammad;Jacob, Alan R.;Jamali, Safa;Hsiao, Lilian C.
• 通讯作者: Hsiao, Lilian C.

Hydrodynamic origin for the suspension viscoelasticity of rough colloids

粗糙胶体悬浮粘弹性的流体动力学起源

• DOI: 10.1122/8.0000424
• 发表时间: 2022
• 期刊: Journal of Rheology
• 影响因子: 3.3
• 作者: Pradeep, Shravan;Wessel, Alan;Hsiao, Lilian C.
• 通讯作者: Hsiao, Lilian C.