Since the inception of digital microfluidics, the synthesis problems of scheduling, placement and routing have been performed offline (before runtime) due to their algorithmic complexity. However, with the increasing maturity of digital microfluidic research, online synthesis is becoming a realistic possibility that can bring new benefits in the areas of dynamic scheduling, control-flow, fault-tolerance and live-feedback. This paper contributes to the digital microfluidic synthesis process by introducing a fast, novel path-based scheduling algorithm that produces better schedules than list scheduler for assays with high fan-out; path scheduler computes schedules in milliseconds, making it suitable for both offline and online synthesis. © 2012 ACM.