RUI: Multiscale Analysis of Adhesion and Friction Coupling Enabled by Bio-Inspired Anisotropic Fibrillar Adhesives

非技术概述自然界中的许多生物体已经将微观毛发和原纤维改造成用于运动目的和/或确保牢固附着的坚固粘合剂。壁虎是研究最多的物种之一，由于它们相当大的身体尺寸和复杂的脚趾垫结构，用于开发生物启发的干粘合剂。尽管粘合强度有了很大的改进，但许多实验室规模的“原理证明”人造粘合剂的耐用性和可重复使用性仍然落后于天然粘合剂，即使在更光滑和更清洁的基材上进行测试。在这个项目中，控制接触形状和几何形状的粘合剂阵列将使用模板辅助铸造成型和先进的微加工技术制造。粘附行为将被表征为同时测量非理想条件下的粘附和摩擦（例如，在非无尘表面上，以及在不同的温度和湿度下）。将进行计算机模拟来解释实验结果。总的来说，所提出的工作提供了一种替代方法来研究先进的智能上层建筑模仿自然的表面和界面现象。学生将研究工程，材料科学，物理，化学和其他相关学科的交叉点的问题。通过建立最先进的多功能机械系统和仿真工具来探索广泛的应用，将大大提高研究生产力，并为加州州立大学洛杉矶分校和南加州地区的本科生和研究生提供必要的研究培训。该教育计划有助于加州州立大学洛杉矶分校教育当地少数民族和代表性不足的学生成为下一代工程师，科学家和教育工作者的悠久传统，他们的愿景是将科学优先事项与解决社会问题联系起来。ppTECHNICAL summary模仿壁虎趾垫结构和功能的努力寻求开发一类新的高级粘合剂，其不仅是粘性的和容易分离的，而且是不结垢的。目前的合成干粘合剂具有大的所需预加载和对多尘环境的耐受性，这显著限制了它们用于粘附或操纵易碎和非无尘物体的用途。该项目的重点是了解各向异性纤维状粘合剂单元的接合和脱离机制，其具有多种接触形状/几何形状和结构/材料梯度，跨越多个长度和时间尺度。所提出的干粘合剂设计结合了在刚毛水平处观察到的几何各向异性和在抹刀水平处刚毛分支的特殊接触形状。最终的目标是阐明粘附力和摩擦力是如何耦合的，并且可以通过合理设计几何形状相关的干胶单元来更好地控制。将使用定制设计的表面力装置在循环载荷和非无尘环境以及不同温度和相对湿度下评估粘合剂性能。将实施多尺度各向异性有限元粘结区建模，以参数化接触形状相关的界面行为，并分析粘结机制，断裂和失效。该项目将在仿生研究方面产生基础和应用方面的进展，例如，开发可切换和自清洁表面;微/纳米操纵;以及用于机器人、能源和生物医学应用的高耐受性干胶和药物输送系统。pp该奖项反映了NSF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。/ p

pNON-TECHNICAL SUMMARYMany organisms in nature have adapted microscopic hairs and fibrils as robust adhesives for locomotion purposes and/or securing a strong attachment. Geckos are among the most studied species for developing bio-inspired dry adhesives due to their fairly large body size and sophisticated toe pad structure. Despite great improvements on adhesion strength, the durability and reusability of many lab-scale 'proof-of-principle' artificial adhesives still lag behind their natural counterparts, even being tested on smoother and cleaner substrates. In this project, adhesive arrays with controlled contact shapes and geometries will be fabricated using template-assisted cast molding and advanced micro-fabrication techniques. Adhesive behavior will be characterized to simultaneously measure adhesion and friction under non-idealized conditions (e.g., on non-dust-free surfaces, and at different temperatures and humidity). Computer simulation will be performed to explain the experimental results. Overall, the proposed work provides an alternative approach to study surface and interfacial phenomena of advanced smart superstructures mimicking nature. Students will examine problems at the crossroads of engineering, materials science, physics, chemistry, and other related disciplines. Exploring a broad range of applications by building up state-of-the-art versatile mechanical system and simulation tools will substantially enhance research productivity, and provide essential research training to undergraduate and graduate students at Cal State LA and in the Southern California region. The educational plan contributes to Cal State LA's long tradition of educating local minority and underrepresented students to become the next generation of engineers, scientists, and educators whose vision is to link science priorities to the solving of societal problems./ppTECHNICAL SUMMARYEfforts to mimic gecko toe pad structure and function seek to develop a new class of advanced adhesives that are not only sticky and easy to unstick, but also non-fouling. Current synthetic dry adhesives suffer from large required preloading and intolerance of dusty environments, which significantly limit their use for sticking to or manipulating fragile and non-dust-free objects. This project focuses on understanding the engaging and disengaging mechanisms of anisotropic fibrillar adhesive units featuring a variety of contact shapes/geometries and structural/materials gradient across multiple lengths and temporal scales. The proposed dry adhesive design incorporates both the geometrical anisotropy seen at the setal level and the special contact shape of the setal branches at the spatula level. The ultimate goal is to elucidate how adhesion and friction are coupled and may be better controlled by rationally designing the geometry dependent dry adhesive units. Adhesive performance will be evaluated under cyclic loadings and non-dust-free environments, as well as different temperatures and relative humidity, using a custom-designed surface force apparatus. Multiscale anisotropic finite-element cohesive-zone modeling will be implemented to parameterize the contact shape dependent interfacial behaviors, and to analyze the adhesive mechanisms, fracture and failures. This project will yield both basic and applied advances in biomimetic research, e.g., development of switchable and self-cleaning surfaces; micro-/nanomanipulations; and high tolerance dry adhesives and drug delivery systems for robotics, energy and biomedical applications./ppThis 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./p