Trapping of atomic and mesoscopic particles with optical fields is a practical technique employed in many research disciplines. Developing similar trapping methods for self-propelled, i.e. active, particles is, however, challenging due to the typical anisotropic material composition of Janus-type active particles. This renders their trapping with magneto-optical fields to be difficult. Here we present the realization of a motility-trap for active particles, which only exploits their self-propulsion properties. By combining experiments, numerical simulations, and theory, we show that, under appropriate conditions, a force-free rotation of the self-propulsion direction towards the trap's center can be achieved, which results in an exponential localization of active particles. Because this trapping mechanism can be applied to any propulsion scheme, we expect such motility-tweezers to be relevant for fundamental studies of self-driven objects as well as for their applications as autonomous microrobots.

用光场俘获原子和介观粒子是许多研究学科中采用的实用技术。然而，由于Janus型活性颗粒的典型的各向异性材料组成，为自推进即活性颗粒开发类似的捕集方法是具有挑战性的。这使得它们难以被磁光场俘获。在这里，我们介绍了一种用于活性粒子的动力陷阱的实现，该陷阱仅利用了它们的自推进特性。通过结合实验，数值模拟和理论，我们表明，在适当的条件下，可以实现自推进方向朝向捕集阱中心的无力旋转，从而导致活性粒子呈指数分布。