Controlling Friction and Adhesion Using Charged Hydrogel Lubricants During Manufacturing

该基金支持在制造过程中提供与润滑相关的新知识的研究，促进科学进步和促进国家繁荣。油基润滑剂会产生污染物和有害污染物，因此，对可再生的、至少同样有效的环保型润滑剂有需求。虽然在水介质中润滑可以解决这一需求，但由于水粘度的压力系数低等原因，它很少应用于制造。在像软骨这样的生物摩擦系统中，这些挑战可以通过使用凝胶辅助水润滑来解决。受此启发，该项目设计了具有带电水凝胶状结构的合成水性薄膜，可以在制造过程中主动控制摩擦和粘附。主动控制水凝胶润滑不仅可以确保食品，生物医学和制药行业的良好生产规范，低碳足迹和机器部件的可调润滑，而且还可以在制造过程中处理柔软的生物启发材料和精致的电子元件。此外，从本研究中获得的知识允许机器接口动态适应其当前任务，从而提高机器的通用性，效率和产品质量。因此，这项研究的结果有利于美国经济和社会，并有助于将美国制造业扩展到新的应用领域。多学科方法有助于扩大妇女和代表性不足的少数民族学生参与研究，并对工程教育产生积极影响。这项研究产生了通过电调制主动控制水凝胶基润滑的基本知识。特别是，该项目确定了如何调节三种水凝胶系统(1)静电吸引与斥力，（2)氢键与静电斥力，(3)疏水吸引与静电斥力）中物理相互作用之间的平衡，决定了自组装途径和微观结构，以及如何将其应用于调节润滑。这些润滑剂是通过微相分离合成的。实验研究将显微镜、振荡剪切力、法向力和侧向力测量与基于聚合物物理的模型结合起来，以了解物理关联在界面结构和流变学中所起的作用，以及它们如何影响摩擦和粘附。这项研究还推进了化学和电刺激如何驱动摩擦和粘附机制变化的知识。新知识包括在发现水凝胶润滑机制方面的突破，这是通过整合新颖和改进的实验和建模工具集实现的，具有结构-性能关系控制的响应性水凝胶的新设计规则，以及预测摩擦系数作为操作条件和水凝胶成分函数的框架。该奖项反映了美国国家科学基金会的法定使命，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。

This grant supports research that contributes new knowledge related to lubrication in manufacturing processes, promoting both the progress of science and advancing national prosperity. Oil-based lubricants generate pollutants and harmful contaminants and, thus, there is a demand for environmentally benign lubricants that are renewable and, at least, as efficient. While lubrication in an aqueous medium could solve this need, it is rarely applied in manufacturing due to the low pressure-coefficient of the viscosity of water, among other reasons. In biological tribosystems like cartilage, these challenges are met by employing gel-assisted aqueous lubrication. Thus inspired, this project designs synthetic waterborne films with charged hydrogel-like structures that enable the active control of friction and adhesion during manufacturing. Active control of hydrogel lubrication not only ensures good manufacturing practices in food, biomedical and pharmaceutical industries, low-carbon footprint and tunable lubrication of machine components, but also enables handling of soft biologically inspired materials and delicate electronic components during manufacturing. Furthermore, the knowledge derived from this research allows machine interfaces to dynamically adapt to their current task, which increases machine versatility, efficiency and product quality. Therefore, results from this research benefit the U.S. economy and society and help to extend U.S. manufacturing to new application areas. The multi-disciplinary approach helps broaden participation of women and underrepresented minority students in research and positively impacts engineering education.This research produces fundamental knowledge on active control of hydrogel-based lubrication via electrical modulation. In particular, the project determines how modulating the balance between physical interactions in three hydrogel systems, (1) electrostatic attraction vs. repulsion, (2) hydrogen bonding vs. electrostatic repulsion, and (3) hydrophobic attraction vs. electrostatic repulsion), dictates the self-assembly pathway and microstructure, and how this can be applied to modulate lubrication. These lubricants are synthesized via microphase separation. The experimental studies combine microscopy, oscillatory shear and normal and lateral force measurements with polymer physics-based models to deliver understanding of the role played by physical associations in the interfacial structure and rheology and how they influence friction and adhesion. This research also advances the knowledge about how chemical and electrical stimulation drives changes in friction and adhesion mechanisms. The new knowledge includes breakthroughs in discovery of hydrogel lubrication mechanisms enabled by the integration of novel and improved experimental and modeling toolsets, novel design rules for responsive hydrogels with control over the structure-property relationships, and a framework to predict the friction coefficient as a function of the operating conditions and hydrogel composition.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.