Water-Immersed Polymer Interfaces and the Role of their Interfacial Properties on Bio-Interfacial Forces

（CBET- 0651983 / Notre Dame U. / Zhu，Y.）具有可调界面力的响应性聚合物生物界面这个与纳米生物相关的项目解决了理解生物流体浸没的聚合物薄膜对生物润滑的界面性质的作用的科学和工程挑战。虽然该项目侧重于基础知识，但PI考虑到与聚合物界面相互作用相关的生物医学工程应用，这些应用是生物系统中减少摩擦和防止磨损的基础，例如移动软骨关节和生物相容性和非生物污垢涂层的开发。具体而言，该提案旨在了解生物软组织中的超润滑机制，并超越这一点，通过明智地选择表面化学和粘弹性以及施加的外部刺激来操纵合成聚合物生物界面的超低摩擦响应。本研究的近期目标是：1）表征浸没在生物流体中的聚合物薄膜的界面特性，并探讨在可变形的聚合物生物界面上可能引起升力以减少磨损的法向力和摩擦力的耦合：2）阐明在对比硬界面上生物润滑行为的差异;和3）解决温度、表面末端官能度和吸附的蛋白质对水性介质中聚合物界面处的界面力的作用。拟议的研究将集中在水溶液，包括模拟体液，润滑素和滑液的界面：1）低弹性聚合物刷状涂层，聚（N-异丙基丙烯酰胺），其相和粘弹性行为是热和化学可调的，和2）自组装单分子层（SAM），其中表面疏水性和蛋白质亲和力系统地变化，以控制摩擦。了解分子结构如何赋予特定的界面力和仿生界面的动态特性将增强我们对滑膜关节润滑，关节炎或慢性关节症状的了解，以及具有最佳界面特性的智能聚合物薄膜的工程。这将是第一次，界面生物膜的结构-流变学关系可以通过PI实验室中的一种新型实验装置，通过同时进行的显微镜和界面力测量来破译。独特的相关facilityintegrates一个界面力装置与共聚焦显微镜，同时测量界面力和可视化的三维瞬态微观结构动态的基础聚合物薄膜由于外部刺激。它提供了一个新的分子方法来研究生物润滑机制在软生物大分子界面。其技术意义还包括开发具有优化界面性质的智能生物薄膜的新的分子设计范例。研究具有受限流体薄膜的软界面上的界面力和微观结构之间的相互作用具有重要的科学意义，不仅在基础摩擦学科学中，而且在许多领域，包括微流体、药物输送和生物医学设备。一个基础广泛的教育/推广计划是与这个跨学科的研究计划相结合。PI已经活跃在工程妇女协会（SWE）的地方分会，致力于招聘和留住在许多工程学科中仍然代表性不足的女学生。PI还积极参加与邻近的圣玛丽学院的共同交流方案，这是一所在教育女学生方面领先的私立天主教女子大学。该提案的核心是课程开发和研究指导，以加强圣母大学的生物分子工程项目。最后，该项目旨在与润滑剂和汽车行业（如福特汽车和埃克森美孚）以及印第安纳州活跃的整形外科行业建立强大的联盟，以帮助学生、科学家和工程师就界面润滑剂的分子设计进行交流和互动。

(CBET- 0651983 / Notre Dame U. / Zhu, Y.)Responsive Polymeric Biointerfaces with Tunable Interfacial ForcesThis nano-bio-related project addresses the science and engineering challenge of understanding the role of interfacial properties of biological fluid-immersed polymeric thin films on biolubrication. While this project focuses on fundamentals, the PI has in mind biomedical engineering applications related to polymer interfacial interactions that underlie friction reduction and wear prevention in biological systems such as moving cartilage joints and the development of biocompatible and non-biofouling coatings. Specifically, this proposal aims to understand the superlubricity mechanism in biological soft tissues, and to go beyond this to manipulate the ultra-low friction responses of synthetic polymeric biointerfaces on demand by judicious choice of surface chemistry and viscoelasticity, as well as imposed external stimuli. The immediate objectives of this research are: 1) to characterize interfacial properties of polymer thin films immersed in biological fluids and to probe the coupling ofnormal and frictional forces at deformable polymeric biointerfaces that possibly induce lift to reduce wear; 2) to elucidate how the biolubrication behavior differs at contrasting hard interfaces; and 3) to address the roles of temperature, surface end-functionality and adsorbed protein on interfacial forces at polymer interfaces in aqueous media. The proposed research will focus on aqueous solutions including simulated body fluids, lubricin and synovial fluids at interfaces of: 1) a low-elastic polymer brush-like coating, poly (N-isopropylacrylamide) whose phase and viscoelastic behaviors are thermally and chemically tunable, and 2) self-assembled monolayers (SAM) where surface hydrophobicity and thus protein affinity are systematically varied to control the friction.Intellectual Merit. Understanding how molecular structure endows specific interfacial forces and dynamic properties of biomimetic interfaces would enhance our knowledge of synovial joint lubrication, arthritis or chronic joint symptoms, as well as the engineering of intelligent polymeric thin film with optimal interfacial properties. It will be the first time that the structure-rheological relationship of interfacial biofilms can be deciphered with concurrent microscopic and interfacial force measurements by a novel experimental setup in the PI's lab. The unique correlated facilityintegrates an interfacial force apparatus with a confocal microscope to simultaneously measure interfacial forces and visualize 3-dimensional transient microstructure dynamics of the underlying polymer films due to external stimuli. It offers a new molecular approach to examine biolubrication mechanisms at soft biomacromolecular interfaces. The technical significance also includes thedevelopment of new molecular design paradigm for intelligent biological thin films with optimized interfacial properties. The study of the interplay between interfacial forces and microstructure on soft interfaces with a confine fluid thin film is scientifically important, not only in basic tribology science, but in a number of areas including microfluidics, drug delivery and biomedical devices.Broader Impact. A broad-based education/outreach program is integrated with thisinterdisciplinary research program. Already active in the local chapter of the Society of Women in Engineering (SWE), the PI is committed to the recruitment and retention of female students who continue to be under-represented in many engineering disciplines. The PI also actively participates in a co-exchange program with the neighboring St. Mary's College, a leading private woman's Catholic University in educating woman students. Central to this proposal is curriculum development and research mentoring to strengthen the biomolecular engineering program at Notre Dame. Finally, this project seeks to establish a strong coalition with the lubricant and automotive industries such as Ford Motor and ExxonMobil, and Indiana's active orthopedic industry to help students, scientists and engineers communicate and interact on molecular design of interfacial lubricants.