As soft aqueous hydrogels have moved from new materials to the basis for real engineered devices in the last 20 years, their surface friction and lubrication are emerging as critical aspects of their function. The flexibility to alter and augment their mechanical and surface properties through control of the crosslinked 3D polymer networks has produced materials with diverse surface behaviors, even with the relatively simple composition of a single monomer and crosslink chemistry. Correspondingly with new understandings of the bulk behavior of hydrogels has been the identification of the mechanisms that govern the lubricity and frictional response under dynamic sliding conditions. Here we review these efforts, closely examining and identifying the internal and external influences that drive tribological response in high water content crosslinked hydrogels. The roles of surface structure, elasticity, contact response, charge, water interaction and water flow are addressed here as well as current synthesis and testing methods. We also collect open questions as well as the future needs to fully understand and exploit the surface properties of hydrogels for sliding performance.

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评论：高含水量的交联水凝胶的摩擦和润滑

在过去的20年中，随着软水凝胶从新材料发展成为实际工程设备的基础，其表面摩擦和润滑已成为其功能的关键方面。通过控制交联的3D聚合物网络来灵活地改变和增强其机械和表面性能，即使具有相对简单的单一单体组成和交联化学性质，其材料也具有多种表面行为。与对水凝胶的整体行为的新认识相对应的是，确定了在动态滑动条件下控制润滑性和摩擦响应的机理。在这里，我们回顾这些努力，仔细检查并确定在高含水量交联水凝胶中驱动摩擦响应的内部和外部影响。本文讨论了表面结构，弹性，接触响应，电荷，水相互作用和水流的作用以及当前的合成和测试方法。我们还收集未解决的问题以及未来的需求，以充分理解和利用水凝胶的表面特性来提高滑动性能。

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