Lubrication is critical to the success of total joint replacement. Despite significant progress in the understanding of molecular tribology for chemical systems, there is still a lack of a fundamental understanding of the lubrication mechanisms for joints and other biological systems. Currently, the most common solution to arthritis is total joint replacement. However, the biocompatibility of implanted materials poses a great challenge. Poly(ethylene glycol) (PEG) and zwitterionic-based materials are two commonly used biocompatible materials. It is hypothesized that zwitterionic-based coatings will have very low friction. In this work, friction between two surfaces covered by zwitterionic polymer brushes will be studied using both non-equilibrium molecular dynamics simulations and chemical force microscopy experiments. The objectives of this work are to gain insights into the origin of the friction between zwitterionic coatings at the molecular level, to establish the relationship between nano-scale friction and surface hydration, and to compare the performance of three unique zwitterionic coatings. PEG will also be studied for comparison. The success of this work will provide a fundamental understanding of the interfaces encountered in bionanotribology and will guide the design of new biocompatible materials for applications in artificial joints and BioMEMS/NEMS. The outcome of this work is to identify and design coatings with both low friction and high compatibility. Graduate and undergraduate students will be involved in this project, particularly those from underrepresented groups. As a part of the ongoing undergraduate curriculum reform, the PI is teaching a new course on ?Biomolecular Interfaces? and will teach a new undergraduate thermodynamics course which will integrate classical thermodynamics, statistical mechanics and molecular simulation. Results from the proposed work will contribute significantly to these two new courses. The knowledge will also be disseminated through several other courses that the PI gives lectures to every year.
