Timing and synchronization of droplets on ratchet conveyors

We report on a novel anisotropic ratchet conveyor (ARC) system that can transport liquid droplets using silicon dioxide (SiO
₂
) patterns and applied vibrations. We have discovered that the threshold acceleration amplitude can be modulated by a transition in the duty cycle of recurring SiO
₂
features. From this observation we have developed `droplet gates', or devices that can selectively pause droplet motion. These devices are essential for timing, synchronization, and mixing of droplets in automated ARC systems.