Abstract
<jats:p>Interacting droplets provide a promising route towards adaptive matter capable of autonomous transport, organization and reconfiguration. Realizing such systems, however, requires mechanisms that balance attractive and repulsive forces without continuous external control. Here, we present a liquid robotic platform based on filamentous assemblies that, analogous to handover processes in conventional robotic systems, can capture, transfer and position cargo droplets. Central to the design is the spatial separation of force-generating actuator droplets (immersed in the aqueous phase) and oil-based cargo droplets (moving over the water surface) that are actuated by these forces. Surfactant-based actuator droplets grow myelin filaments towards the surface, enabling them to catch and retain floating oil droplets. A unique symmetry breaking mechanism arises with multiple actuators, which allows for the directional handover of cargo droplets from actuator to actuator along arrays through a combination of Marangoni flow, Marangoni backflow and surfactant self-assembly. Furthermore, non-merging droplets are designed that cluster and form raft-like assemblies whose spatial positioning can be directed by squared actuator arrays. Importantly, the actuator droplets can be deposited robotically in programmable patterns, enabling the on-demand definition of pathways and targets: Providing a versatile strategy for adaptive and reconfigurable liquid robotic systems.</jats:p>