(43c) Turning Passive Particles into Active Motion with Surface Heterogeneity

Active particles have attracted increasing interests in the past decades, due to their ability to self-propel and the potential for collective behavior. The self-propelling motion relies on heterogeneity, either from the asymmetry of the particle themselves, or from the gradient in the local environment. When the driving mechanism comes from the environment while the particle is homogeneous, the particle only migrates when the local gradient is strong enough, thus enables sensing of the environmental changes. The local gradient can be designed such that the particle motion follows a specific trajectory to the target area. Here, we design a surface with charge density gradient to drive nearby homogeneously charged particles. The particles have modified surface chemistry such that a solute concentration gradient is generated radially and migrate along the surface charge gradient diffusiophoretically. The physical mechanism for the particle motion is unveiled. Different charge density patterns are designed to demonstrate various particle trajectories and speed. This unique system opens new avenues to sense the surface heterogeneity and harness it for targeted cargo delivery.