Effect of Surface Stiffness on the Friction of Confined Microgel Liquids

表面刚度对受限微凝胶液体摩擦的影响

• 批准号: 1761418
• 负责人: Yingxi Elaine Zhu
• 金额: $ 37.27万
• 依托单位: Wayne 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: 2018-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1761418&HistoricalAwards=false
• 关键词: Effect; Surface; Stiffness; Friction; Confined

This grant will impact progress of science and advance the national health and prosperity by researching the properties of liquids tightly confined between 'soft' walls often found in biological systems and in nanostructures impacted nanotechnology. A liquid tightly confined between two solid surfaces at a gap spacing comparable to its molecular dimension can behave very different from its bulk state. Increased friction is commonly observed with confined liquids, often due to the solidification of the liquid when confined. Prior research of confined liquids has mostly focused on hard and well-structured confining walls. Yet many biological and engineering processes involve highly soft and deformable surfaces, such as lubrication between synovial and cartilaginous joints, motions of red blood cells in capillaries, and even the aquaplaning of rubbery tires. The impact of surface stiffness on fluid lubrication remains poorly understood. This grant supports fundamental research to understand the effect of surface stiffness on the structure and friction of strongly confined liquids, whose confining wall stiffness can be varied to be relevant of many real world systems. The knowledge gained from this investigation can be transformed to control fluid transport by optimizing surface mechanical elasticity and design low-friction interfaces for energy saving in various industrial applications. Broader impacts of this project will also include the recruitment and training of underrepresented students, including women students, as the next generation of American engineers. This project addresses the long-debated questions of surface-induced glass transition and friction augment of spatially confined liquids. A quantitative understanding of the effect of surface stiffness on the dynamics of confined liquids between deformable surfaces will be developed by in-situ microscopic characterization at a single-particle level. The surface-to-liquid stiffness ratios will be tuned in a single microgel system by using microgel particles of varied crosslinking degrees as both surface coatings and confined liquids. A micron-gap tribometer integrated with confocal laser scanning microscopy enables the measurement of the heterogeneous dynamics and friction of confined microgel liquids between two deformable surfaces against varied gap spacings and shear conditions. The relationship among surface stiffness, confinement length scales, dynamic heterogeneity, and shear-induced fluidity of confined liquids will be quantified. The results obtained from this research will give molecular insight to confinement-induced glassy dynamics and biolubrication involving highly deformable surfaces. The success of this project can lead to a new avenue by judicious design and control of the mechanical compliance of surfaces and coatings to modify friction, facilitate interfacial mass transport, and manipulate surface sensing and actuation.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.

这项拨款将影响科学的进步，并通过研究紧密限制在生物系统和纳米结构中经常发现的“软”壁之间的液体的性质来促进国家的健康和繁荣。一种液体被紧密地限制在两个固体表面之间，其间隙间距与其分子尺寸相当，这种液体的行为与其体相态非常不同。在受限的液体中通常观察到增加的摩擦，这通常是由于液体在受限时的固化。先前对受限液体的研究主要集中在坚硬且结构良好的限制壁上。然而，许多生物和工程过程涉及高度柔软和可变形的表面，例如滑液和软骨关节之间的润滑，毛细血管中红细胞的运动，甚至橡胶轮胎的滑水。表面刚度对流体润滑的影响仍然知之甚少。该补助金支持基础研究，以了解表面刚度对强约束液体的结构和摩擦的影响，其限制壁刚度可以变化到与许多真实的世界系统相关。从这项研究中获得的知识可以通过优化表面机械弹性和设计低摩擦界面来控制流体传输，以在各种工业应用中节省能源。这一项目的更广泛影响还将包括招聘和培训代表性不足的学生，包括女学生，作为下一代美国工程师。本计画针对空间受限液体之表面诱导玻璃化转变及摩擦增加等长期争议的问题。一个定量的了解的表面刚度对可变形表面之间的封闭液体的动力学的影响，将开发在一个单一的颗粒水平的原位微观表征。通过使用不同交联度的微凝胶颗粒作为表面涂层和受限液体，将在单个微凝胶系统中调节表面与液体的刚度比。集成了共聚焦激光扫描显微镜的微米间隙摩擦计能够测量两个可变形表面之间的受限微凝胶液体对不同间隙间距和剪切条件的非均匀动力学和摩擦。表面刚度，约束长度尺度，动态不均匀性和剪切引起的流动性的约束液体之间的关系将被量化。从这项研究中获得的结果将提供分子洞察力的约束诱导的玻璃态动力学和生物润滑涉及高度可变形的表面。该项目的成功可以通过明智的设计和控制表面和涂层的机械顺应性来改善摩擦，促进界面质量传输，操纵表面传感和驱动，从而开辟一条新的途径。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Ultrastructure of Critical-Gel-like Polyzwitterion–Polyoxometalate Complex Coacervates: Effects of Temperature, Salt Concentration, and Shear

临界凝胶状聚两性离子-多金属氧酸盐复合凝聚层的超微结构：温度、盐浓度和剪切力的影响

• DOI: 10.1021/acs.macromol.0c01618
• 发表时间: 2020
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Jing, Benxin;Ferreira, Manuela;Lin, Kehua;Li, Ruipeng;Yavitt, Benjamin M.;Qiu, Jie;Fukuto, Masafumi;Zhu, Yingxi
• 通讯作者: Zhu, Yingxi