Interfacial Mechanics and Contact Properties of Model Membranes

模型膜的界面力学和接触特性

• 批准号: 0525645
• 负责人: Kenneth Shull
• 金额: $ 35.4万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0525645&HistoricalAwards=false
• 关键词: Interfacial; Mechanics; Contact; Properties; Model

Summary and Intellectual MeritA group led by the PI will develop a highly sensitive adhesion experiment designed to assessthe interactions between well characterized model surfaces in water. The measurement is basedon the contact between a synthetic polymer membrane and a quartz crystal resonator. Themembrane consists of an elastic layer at the air/water interface, and is an excellent model for avariety of materials ranging from synthetic polymer gels to living tissues. The membranesurface and the surface with which it interacts will both be coated with molecules that aredesigned to eliminate non-specific background adhesion between the two surfaces. Specificadhesion molecules will then be added to both surfaces, and the adhesion energy will be relatedto the interaction potential of the individual bonds, and to their surface concentration. Theexperiments are conceptually similar to dewetting experiments, with contact of the membraneand the surface corresponding to a region where water has been largely excluded from betweenthe contacting surfaces. The experimental geometry is designed to give sensitivity to very smallcontact angles, and hence to very small adhesive interactions. Membrane elasticity serves twoimportant functions. The first of these is to extend the range of adhesive interactions that can beprobed so that the molecular origins of mechanical toughness of soft, highly deformablematerials can be thoroughly investigated. The second function of membrane elasticity is toprovide a means for fixing the adhesive molecules in place while isolating the system from thesurrounding air environment so that the surfaces remain hydrated, even while in mechanicalcontact with one another. A detailed mechanical analysis will be developed for cases where theadhesion energy is large enough so that elastic effects must be taken into account. Additionalinformation about the nature of the mechanical contact will be obtained by monitoring thefrequency shift and dissipation of the quartz crystal resonators in the vicinity of a mechanicalresonance of the crystal. The experimental methodology can be applied to a wide variety ofadhesion problems in polymer physics and in biology, but experiments will begin with studiesutilizing adhesive molecules that are very well characterized at the single molecule level.Broader ImpactsThe PI has developed a unique online multimedia text in polymer science that will undergocontinued revision during this funding cycle. Additional contributions to undergraduate andundergraduate education will result directly from the proposed work, with three Ph.D. studentsand between 6 and 8 undergraduate students being trained in various aspects of mechanics,polymer physics and polymer synthesis. International experience will also be obtained as part ofa collaboration with Prof. Diethelm Johannsmann at the University of Clausthal in Germany.Two Ph.D. students will conduct research in the Johannsmann laboratory during the course ofthis project, and two students from the Johannsmann laboratory will visit the PI's lab atNorthwestern. Existing outreach activities will continue at local high schools and middle schoolsin Evanston and Chicago. The enhancements in mechanical characterization capabilitiesresulting from the proposed work will benefit a variety of research groups at Northwestern, inaddition to scientists and engineers at local companies who utilize the micromechanics labsupervised by the PI. The broader scientific impact of the work will be felt most strongly in thebiomaterials community, by providing a means for quantifying adhesion in practically relevantbiological systems that are amenable to the membrane geometry.

摘要和智力优势由PI领导的一个小组将开发一个高灵敏度的粘附实验，旨在评估水中良好表征的模型表面之间的相互作用。该测量是基于合成聚合物膜和石英晶体谐振器之间的接触。这种膜在空气/水界面上有一个弹性层，是从合成聚合物凝胶到活组织等各种材料的极好模型。膜的表面和与之相互作用的表面都将涂上分子，这些分子被设计用来消除两个表面之间的非特异性背景粘附。然后，特定的粘附分子将被添加到两个表面上，粘附能将与各个键的相互作用势以及它们的表面浓度相关。该实验在概念上类似于去湿实验，膜和表面的接触对应于其中水已在很大程度上被排除在接触表面之间的区域。实验几何形状的设计是为了给非常小的接触角的灵敏度，因此非常小的粘合剂相互作用。膜的弹性有两个重要的功能。其中第一个是扩大范围的粘合剂相互作用，可以探测，使软，高度deformablematerials的机械韧性的分子起源可以彻底调查。膜弹性的第二个功能是提供一种将粘合剂分子固定在适当位置的方法，同时将系统与周围的空气环境隔离，使得表面即使在彼此机械接触时也保持水合。一个详细的力学分析将开发的情况下，theadhesion能源是足够大，弹性效应必须考虑在内。关于机械接触的性质的附加信息将通过监测在晶体的机械谐振附近的石英晶体谐振器的频移和耗散来获得。实验方法可以应用于各种各样的粘附问题，在聚合物物理学和生物学，但实验将开始与studiesutilizing粘性分子，是非常好的特点，在单分子水平。更广泛的影响PI已经开发了一个独特的在线多媒体文本聚合物科学，将在本资金周期持续修订。额外的贡献，本科和本科教育将直接从拟议的工作，与三个博士学位。在力学、高分子物理和高分子合成等各个方面培训了100名学生和6至8名本科生。作为与德国克劳斯塔尔大学Diethelm Johannsmann教授合作的一部分，还将获得国际经验。学生们将在Johannsmann实验室进行研究，两名来自Johannsmann实验室的学生将参观PI在西北大学的实验室。现有的外展活动将继续在埃文斯顿和芝加哥的当地高中和中学进行。从拟议的工作中产生的机械表征能力的增强将使西北大学的各种研究小组受益，此外还有当地公司的科学家和工程师，他们利用PI监督的微观力学实验室。这项工作的更广泛的科学影响将在生物材料界感受到最强烈的，通过提供一种手段，量化粘附在实际相关的生物系统，是服从膜的几何形状。