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 (SiO2) patterns and applied vibrations. We have discovered that the threshold acceleration amplitude can be modulated by a transition in the duty cycle of recurring SiO2 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.