Simulations of hydration lubrication between surfaces

水合润滑是指极表面之间的一系列与生物和技术相关的润滑现象，其特征是摩擦系数极低。它起源于围绕局部表面电荷形成的强结合水化层。这些水化层提供了非凡的润滑性能，也可以抵抗大负荷。近十年来的实验发现还有待于深入的理论解释和理解。为了阐明这一现象的内在机制，我们提出了一种基于原子模型的水化润滑现象的研究。我们计划将非平衡流动以及平衡模拟与我们的新技术相结合，这些技术能够在规定的水化学势下确定准确的水合水平。在第一部分中，我们考虑具有可控的极性和刚度的简单平面曲面，这允许系统地研究摩擦力的基本原理。我们用实验相关的磷脂膜在液体和凝胶相中进行了研究。我们打算通过研究基于氢键动力学、水序参数和膜结构的潜在微观机制来补充结果。

Hydration lubrication describes a biologically and technically relevant range of lubrication phenomena between polar surfaces, characterized by an ultralow friction coefficient. It originates from strongly bound hydration layers formed around local surface charges. These hydration layers provide extraordinary lubrication properties that can resist also large loads. The experimental discoveries in the recent decade are still awaiting for thorough theoretical explanations and understanding. In order to illuminate the underlying mechanisms, we propose a study of the hydration lubrication phenomenon in terms of atomistic modeling. We plan to combine non-equilibrium flow as well equilibrium simulations with our novel techniques that enable to determine the exact hydration level at prescribed water chemical potential. In the first part we consider simple planar surfaces with controllable degrees of polarity and stiffness, which allows for a systematic study of the fundamental principles of friction forces. We proceed the study with experimentally relevant phospholipid membranes in fluid as well as gel phases. We intend to complement the results by investigating the underlying microscopic mechanisms based on hydrogen bonding dynamics, water order parameters, and membrane structure.