RUI: The Origins of Statistical Variation of Strength in Micropatterned Adhesive Contacts

该研究旨在研究真实世界表面粗糙度特性与新型可控和可重复使用的粘合剂表面性能之间的关系。基于具有微尺度结构阵列的图案化表面，从昆虫和蜥蜴的脚趾垫中获得灵感，这些粘合剂可以在许多重复循环中在牢固的附着和容易的分离之间过渡。这可以实现在极端环境中（例如在真空和水下）抓握精细物体或创建多功能界面（例如在生物医学诊断和治疗中）的新能力。每个微图案化子接触处的界面缺陷的差异导致局部粘合剂性能的变化，其中统计特性影响粘合剂贴片的整体强度和稳定性。这项工作将建立的关系，使新兴的统计行为和由此产生的粘合剂性能的预测，基于接触表面的特性。这笔赠款还将加强加州州立大学北岭分校机械工程学生的研究教育活动，其中65.6%来自传统上服务不足的少数民族。将通过一个以课程为基础的本科项目来扩展该范围，使大量学生能够为实现研究目标贡献有意义的数据。 此外，参与的学生将担任本科生导师，并围绕这一主题举办高中外展研讨会。本研究将解决理解方面的几个关键差距。仅针对理想化缺陷表征了子触点的粘合强度，并且将考虑缺陷尺寸、形状和位置的全面范围。微观结构分离的内聚区有限元模拟将提供强度，因为缺陷性质是变化的。粗糙表面上的缺陷形成尚不清楚，必须进行检查，以将表面特性与粘合强度的统计分布联系起来。分子动力学模拟将产生接触地图的光谱性质的粗糙度和弹性性质的机构是不同的。将在具有制造缺陷和随机粗糙度的表面上进行微图案化粘合剂的实验表征，以验证通过建模和模拟获得的关系。最后，了解统计变化的影响，在亚接触粘合强度的性能，在长度和时间尺度近似临时粘接应用必须扩大。 一个半分析力学模型的胶粘剂补丁的行为将整合这种局部变化，并检查基板曲率的综合影响，加载速率，和补丁的大小对全球胶粘剂performance.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This grant investigates the relationship between the properties of roughness on real-world surfaces and the resulting performance of novel controllable and reusable adhesive surfaces. Based upon patterning surfaces with arrays of microscale structures, taking inspiration from the toepads of insects and lizards, these adhesives can transition between strong attachment and easy detachment over many repeat cycles. This may enable new capabilities in gripping of delicate objects in extreme environments (e.g. in vacuum and underwater) or in the creation of multifunctional interfaces (e.g. in biomedical diagnostics and therapeutics). Differences in interfacial defects at each micropatterned sub-contact results in variation in local adhesive performance, with the statistical properties influencing the global strength and stability of the adhesive patch. This work will establish relationships which enable prediction of the emerging statistical behavior and resulting adhesive performance, based upon characteristic properties of the contacting surfaces. This grant will also strengthen research-based educational activities for the Mechanical Engineering student body at California State University Northridge, of whom 65.6 percent are from traditionally underserved minorities. The reach will be extended through a course-based undergraduate project, allowing a large volume of students to contribute meaningful data toward achieving the research objectives. Additionally, participating students will serve as undergraduate mentors and run high school outreach workshops themed around the topic.Several key gaps in understanding will be addressed in this study. The adhesive strength of sub-contacts has only been characterized for idealized defects, and a comprehensive range of defect size, shape, and position will be considered. Cohesive zone finite element simulations of microstructural detachment will provide the strength as defect properties are varied. Defect formation on rough surfaces is not understood, and must be examined to relate the surface characteristics to the statistical distribution of adhesive strength. Molecular dynamics simulations will yield contact maps as spectral properties of the roughness and the elastic properties of the bodies are varied. Experimental characterization of micropatterned adhesives will be performed on surfaces with manufactured defects and random roughness to validate relationships obtained through modeling and simulation. Lastly, understanding of the influence of statistical variation in sub-contact adhesive strength on performance at length and time scales approximating temporary bonding applications must be expanded. A semi-analytical mechanical model of adhesive patch behavior will integrate this local variation and examine the combined effects of substrate curvature, loading rate, and patch size on the global adhesive performance.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.