It has been known for more than 200 years that the maximum static friction force between two solid surfaces is usually greater than the kinetic friction force—the force that is required to maintain the relative motion of the surfaces once the static force has been overcome. But the forces that impede the lateral motion of a drop of liquid on a solid surface are not as well characterized, and there is a lack of understanding about liquid–solid friction in general. Here, we report that the lateral adhesion force between a liquid drop and a solid can also be divided into a static and a kinetic regime. This striking analogy with solid–solid friction is a generic phenomenon that holds for liquids of different polarities and surface tensions on smooth, rough and structured surfaces.

已有200多年的历史了，两个固体表面之间的最大静摩擦力通常大于动摩擦力。动静摩擦力是克服静力后保持表面相对运动所需的力。但是阻碍液体在固体表面上的横向运动的力并没有得到很好的表征，而且通常对液-固摩擦也缺乏了解。在这里，我们报告液滴和固体之间的横向粘附力也可以分为静态和动态范围。这种与固-固摩擦的惊人比喻是一种普遍现象，适用于在光滑，粗糙和结构化表面上具有不同极性和表面张力的液体。