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

(CBET-0651983/Notre Dame U/朱，Y.)具有可调谐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了解生物流体浸泡聚合物薄膜的界面属性在生物溶解中的作用这一科学和工程挑战。虽然这个项目关注的是基本原理，但PI考虑到了与聚合物界面相互作用相关的生物医学工程应用，这些相互作用是生物系统(如移动软骨关节)减摩和防磨损的基础，并开发生物兼容和非生物污垢涂层。具体地说，这项建议旨在了解生物软组织中的超润滑性机理，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外部刺激，根据需要操纵合成聚合物生物界面的超低摩擦响应。这项研究的直接目标是：1)表征浸入生物流体中的聚合物薄膜的界面特性，并探索法向力和摩擦力在可变形聚合物生物界面上的耦合，这些力可能会诱导提升以减少磨损；2)阐明在不同的硬界面上生物溶解行为的不同；以及3)研究温度、表面末端官能度和吸附的蛋白质对水介质中聚合物界面界面力的作用。拟议的研究将集中在水溶液中，包括模拟体液、润滑剂和滑液的界面：1)低弹性聚合物刷状涂层，其相和粘弹性行为可以通过热和化学调节的聚(N-异丙基丙烯酰胺)，以及2)自组装单分子膜(SAM)，其中表面疏水性和蛋白质亲和力被系统地改变以控制摩擦。了解分子结构如何赋予特定的界面作用力和仿生界面的动力学性质，将有助于我们加深对滑膜润滑、关节炎或慢性关节症状的了解，以及设计具有最佳界面性能的智能聚合物薄膜。这将是第一次通过PI实验室的一种新的实验装置，通过同时进行微观和界面力测量来破译界面生物膜的结构-流变关系。这种独特的相关设备将界面力仪器与共焦显微镜相结合，可同时测量界面力并可视化底层聚合物薄膜在外部刺激下的三维瞬时微结构动态。它为研究生物大分子软界面上的生物溶解机理提供了一种新的分子方法。其技术意义还包括开发具有优化界面特性的智能生物薄膜的新的分子设计范例。不仅在基础摩擦学领域，而且在微流体、药物输送和生物医疗设备等领域，研究边界流体薄膜软界面上的界面作用力和微观结构之间的相互作用具有重要的科学意义。一个基础广泛的教育/外展计划与这个跨学科研究计划相结合。在工程学妇女协会(SWE)的地方分会中，PI已经很活跃，它致力于招募和留住在许多工程学科中任职人数仍然不足的女学生。该协会还积极参与与邻近的圣玛丽学院的共同交流项目，该学院是一所领先的私立女子天主教大学，教育女学生。这项提议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课程。最后，该项目寻求与福特汽车和埃克森美孚等润滑油和汽车行业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油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.