Antonov Alexander P, Caprini Lorenzo, Ldov Anton, Scholz Christian, Löwen Hartmut
Institut für Theoretische Physik II: Weiche Materie, <a href="https://ror.org/024z2rq82">Heinrich-Heine-Universität Düsseldorf</a>, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Physics Department, <a href="https://ror.org/02be6w209">University of Rome La Sapienza</a>, Piazzale Aldo Moro 5, IT-00185 Rome, Italy.
Phys Rev Lett. 2024 Nov 8;133(19):198301. doi: 10.1103/PhysRevLett.133.198301.
Friction is central to the motion of active (self-propelled) objects such as bacteria, animals, and robots. While in a viscous fluid friction is described by Stokes's law, objects in contact with other solid bodies are often governed by more complex empirical friction laws. Here, we study active particles subject to Coulomb friction using a combination of active granular experiments and simulations, supported by theoretical predictions. The interplay of friction and activity forces induces a rich behavior resulting in three distinct dynamical regimes. While for low activity Brownian motion is recovered, for large activity we observe a dynamical stop and go regime that continuously switches from diffusion and accelerated motion. For greater activity, we observe a supermobile dynamical regime characterized by a fully accelerated motion which is described by an anomalous scaling of the diffusion coefficient with the activity. These findings cannot be observed with Stokes viscous forces typical of active swimmers but are central in dry active objects.
摩擦力是细菌、动物和机器人等主动（自推进）物体运动的核心。虽然在粘性流体中，摩擦力由斯托克斯定律描述，但与其他固体接触的物体通常受更复杂的经验摩擦定律支配。在这里，我们结合主动颗粒实验和模拟，在理论预测的支持下，研究受库仑摩擦作用的主动粒子。摩擦力和活动力的相互作用引发了丰富的行为，导致三种不同的动力学状态。对于低活性，恢复为布朗运动；对于高活性，我们观察到一种动态停止和启动状态，它不断地从扩散和加速运动切换。对于更高的活性，我们观察到一种超移动动力学状态，其特征是完全加速运动，这由扩散系数与活性的反常标度来描述。这些发现无法在主动游动者典型的斯托克斯粘性力中观察到，但在干燥的主动物体中是核心。
