Ring of capillary actuators as trap, tweezers and ratchet for floating particles.

The manipulation of small floating objects represents a crucial step in mesoscale and microfabrication, or the self-aggregation of particles into functional devices. These tiny objects placed at a liquid-air interface interact due to the local liquid slopes created by their menisci. In this study, we present Dipolar Capillary Actuators (DCA), which can modify the local slope of the interface on demand thanks to the magnetic and capillary torque balance. We experimentally characterize these systems and provide a model to describe their ability to alter liquid slopes. These tiny DCA devices can attract or repel a large range of floating particles with various size, shape and wettability. We present a proof-of-concept system comprising six DCAs arranged in a ring that serves as a capillary trap, tweezers, and ratchet.