GOALI/Collaborative Research: Designing Structures to Enhance Friction of Rubbery Materials

橡胶材料与刚性表面的摩擦在许多应用中具有重要的实际意义。例如，它决定了轮胎、挡风玻璃刮水器和密封件的性能和效率。 许多以前的工作控制他们的摩擦机制已经改变了表面化学或橡胶本身的性质改变。 最近对生物附着装置的研究表明，橡胶的附着力也可以通过设计其近表面结构来强烈增强，但通常它们的滑动摩擦力会减少而不是增加。这个资助机会与工业学术联络（GOALI）项目的主要目标是研究表面结构，以增强对粗糙和光滑表面的滑动和静摩擦。 目标应用是改善轮胎的摩擦力，计划中的研究需要在现实约束和条件下进行设计理论、制造和测试。 出于这个原因，该项目是两个大学实验室（康奈尔大学和利哈伊大学）和米其林北美公司的工业研究人员之间的合作。 Lehigh小组负责制造和实验，Cornell小组负责理论和建模，Michelin负责在现实条件和约束下进行测试。 该项目将培养研究生在使用启发和行业相关的合作研究，并将为本科生提供研究机会。 这项研究的结果将被纳入正在进行的合作与达芬奇科学中心在阿伦敦，宾夕法尼亚州，非正式的科学教育。 将为公众设计一个新的展览，介绍生物启发的表面设计，以展示国家在研究和教育方面投资的直接性和影响力。初步工作表明，对于适当设计的一组材料和几何参数，某些表面结构表现出显著的滑动摩擦增强，并保持对粗糙表面的静摩擦增强。例如，膜终止的脊-谷设计（具有方向依赖性摩擦特性的各向异性结构）可以通过耗散能量的复杂内部变形机制来强烈增强在与脊正交的方向上的滑动摩擦。 对于某些参数组合，也可以增强沿着脊的滑动摩擦。 这种膜封端的纤维状结构还导致静摩擦力的强烈增强，其即使在粗糙表面上也基本上保持。 这些受生物启发的表面结构具有通过提供微米级的耗散机制而变革的潜力，该耗散机制可以通过结构的定量设计来优化。

Friction of rubbery materials against a stiff surface is of great practical importance in many applications. For example, it determines the performance and efficiency of tires, windshield wipers, and seals. Much of the previous work on control of their friction mechanisms has either varied surface chemistry or altered properties of the rubber itself. Recent research on biological attachment devices has shown how adhesion of rubbers can also be strongly enhanced by design of their near-surface architecture, but usually their sliding friction is reduced rather than increased. The principal goals of this Grant Opportunity for Academic Liaison with Industry (GOALI)project are to investigate surface architectures for enhancement of sliding and static friction against rough and smooth surfaces. The target application is improving friction of tires, and the planned research requires work on design & theory, fabrication, and testing under realistic constraints and conditions. For this reason, the project is a collaboration between two university labs (at Cornell and Lehigh) and an industrial researcher at Michelin North America. The Lehigh group is responsible for fabrication and experiments, the Cornell group for theory and modeling, and Michelin for testing under realistic conditions and constraints. The project will train graduate students in use-inspired and industry-relevant collaborative research and will provide research opportunities for undergraduate students. The results of this research will be incorporated in an ongoing collaboration with the Da Vinci Science Center in Allentown, PA, for informal science education. A new exhibit will be designed for the general public on bio-inspired design of surfaces to bring out the immediacy and impact of national investments in research and education. Preliminary work has shown that certain surface architectures, for an appropriately designed set of materials and geometrical parameters, exhibit significant enhancement of sliding friction and maintain static friction enhancement against rough surfaces. For example, a film-terminated ridge-valley design (an anisotropic structure with direction-dependent frictional properties) can strongly enhance sliding friction in a direction orthogonal to the ridges by complex internal deformation mechanisms that dissipate energy. For certain combinations of parameters, sliding friction along the ridges can also be enhanced. Such film-terminated fibrillar structures also results in strong enhancement of static friction that is substantially retained even against rough surfaces. These bio-inspired surface architectures have the potential to be transformative by providing dissipation mechanisms at the micron scale that can be optimized by quantitative design of the architecture.