Collaborative Research: Electrotunable and Curvature-Dependent Friction at Nanoscale Contacts Lubricated by Ionic Liquids

有效的摩擦控制在制造过程中至关重要：在宏观制造中，最小化摩擦有助于降低成本；在微制造和超高精密制造中，摩擦控制往往决定着成品的质量和功能。该项目旨在解释离子液体如何润滑介电表面和导电表面之间的单点接触，并研究如何利用表面之间的电势来调节摩擦。该研究将通过原子力显微镜实验和分子模型相结合的方式进行。在该项目中获得的机理见解将有助于改进新型离子液体润滑剂和添加剂的设计。这一进展将有助于提高制造过程的可持续性和效率，从而提高美国工业生产率和竞争力。此外，该合作项目将有助于发展美国的劳动力，扩大未被充分代表的群体对研究的参与，并对工程教育和向工业传播研究产生积极影响。该项目将确定表面曲率、表面电位和由离子液体介导的单粗糙接触摩擦之间的关系。模型系统由原子力显微镜尖端和涂有耐久单层石墨烯的纳米粒子装饰衬底组成，用于量化表面粗糙度和电位对润滑的影响。在严格的分子模拟中，电势被施加在导电表面上，将解析纳米级摩擦系统中离子液体的分子结构和动力学，以阐明电可调摩擦的机制。分子模型和原子力显微镜实验将以一种互补的方式和在可接近的长度尺度上使用，以使分子理解摩擦。通过表面粗糙度和单粗糙接触的电势调节润滑的基本见解将为理解摩擦学行为如何依赖于离子液体和表面的选择提供理论基础。该奖项反映了美国国家科学基金会的法定使命，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。

Effective friction control is crucial in manufacturing processes: in macroscale manufacturing, minimizing friction helps lower costs; in micro-manufacturing and ultra-high precision manufacturing, friction control often determines the quality and functionalities of finished products. This project aims to explain how ionic liquids lubricate single-point contacts between dielectric and conducting surfaces, and to investigate how the friction can be tuned using electrical potential between the surfaces. The research will be conducted by integrating atomic force microscopy experiments and molecular modeling. The mechanistic insight gained in this project will help improve the design of new ionic liquid lubricants and additives. This progress will help improve the sustainability and efficiency of manufacturing processes and thus increase U.S. industrial productivity and competitiveness. Furthermore, the collaborative project will help develop the workforce in the US, broaden the participation of underrepresented groups in research, and positively impact engineering education and the dissemination of research to industry.This project will determine the relationship between surface curvature, surface potential, and friction at single-asperity contacts mediated by ionic liquids. Model systems consisting of atomic force microscopy tips and nanoparticle-decorated substrates coated with durable single-layer graphene will be adopted to quantify the effects of surface roughness and potential on lubrication. Rigorous molecular simulations, in which electrical potentials are imposed on conducting surfaces, will resolve ionic liquids' molecular structure and dynamics in nanoscale tribosystems to elucidate the mechanisms underlying electrotunable friction. Molecular modeling and atomic force microscopy experiments will be used in a complementary manner and at accessible length scales to enable the molecular understanding of friction. The fundamental insights on the modulation of lubrication by surface roughness and electrical potential at single-asperity contacts will provide the theoretical underpinning for understanding how tribological behaviors depend on choices of ionic liquids and surfaces.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.