Briscoe Wuge H, Titmuss Simon, Tiberg Fredrik, Thomas Robert K, McGillivray Duncan J, Klein Jacob
Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK.
Nature. 2006 Nov 9;444(7116):191-4. doi: 10.1038/nature05196.
Boundary lubrication, in which the rubbing surfaces are coated with molecular monolayers, has been studied extensively for over half a century. Such monolayers generally consist of amphiphilic surfactants anchored by their polar headgroups; sliding occurs at the interface between the layers, greatly reducing friction and especially wear of the underlying substrates. This process, widespread in engineering applications, is also predicted to occur in biological lubrication via phospholipid films, though few systematic studies on friction between surfactant layers in aqueous environments have been carried out. Here we show that the frictional stress between two sliding surfaces bearing surfactant monolayers may decrease, when immersed in water, to as little as one per cent or less of its value in air (or oil). We attribute this to the shift of the slip plane from between the surfactant layers, to the surfactant/substrate interface. The low friction would then be due to the fluid hydration layers surrounding the polar head groups attached to the substrate. These results may have implications for future technological and biomedical applications.
边界润滑，即摩擦表面被分子单层覆盖，已经被广泛研究了半个多世纪。这种单层通常由通过其极性头基锚定的两亲性表面活性剂组成；滑动发生在层间界面，大大降低了摩擦力，尤其是底层基材的磨损。这个过程在工程应用中很普遍，据预测在生物润滑中也会通过磷脂膜发生，尽管在水性环境中关于表面活性剂层之间摩擦的系统研究很少。在这里我们表明，当浸入水中时，承载表面活性剂单层的两个滑动表面之间的摩擦应力可能会降低到其在空气中（或油中）值的百分之一或更低。我们将此归因于滑移面从表面活性剂层之间转移到表面活性剂/基材界面。那么低摩擦将归因于附着在基材上的极性头基周围的流体水合层。这些结果可能对未来的技术和生物医学应用有影响。
