Controlling and predicting friction is a significant scientific and technological issue. It is our everyday experience that two smooth surfaces slide more easily over each other than two rough ones, due to interlocking of the rough surfaces. However, the interpretation of such friction forces is difficult since other contributions arise from e.g. adhesion forces, that are harder to control. Here, we demonstrate that designer macroscopic roughness can be used to control, dynamically tune and quantitatively predict friction. We show that the roughness allows to tune the friction coefficient by more than an order of magnitude, which can be explained completely by a simple Coulombic friction model. A kirigami metamaterial surface with externally tunable roughness allows us to show that this understanding of geometrical friction can be used to control on-the-fly the friction in a single system by dynamically controlling its roughness.

控制和预测摩擦是一个重大的科学技术问题。我们的日常经验是，由于粗糙表面的互锁，两个光滑的表面比两个粗糙的表面更容易相互滑动。然而，这种摩擦力的解释是困难的，因为其他贡献来自例如难以控制的粘附力。在这里，我们展示了设计师宏观粗糙度可用于控制、动态调整和定量预测摩擦。我们表明粗糙度允许将摩擦系数调整超过一个数量级，这可以通过简单的库仑摩擦模型完全解释。