Abstract: Embodiments relate to devices, systems, methods and compositions useful for routing and tracking multiple mobile units within a microfluidic device having an inlet channel connected to a multi-way sorting junction, which is fluidly connected with a plurality of 4 or more channels, and a steering mechanism for directing the flow of the mobile units according to a predetermined algorithm. Mobile units can be routed and followed through the microfluidic device in an ordered flow, such that the mobile units are exposed to chemical environments and/or enzymatic synthesis reactions associated with the channels. Mobile units can be steered in multiple directions, between the sorting junctions and the channels by the steering mechanism by changes in flow or pressure. Some such devices, systems, methods and compositions include mobile units that can flow in both the forward and reverse directions and into each of as plurality of 4 or more channels from two sorting junctions.

Abstract: Embodiments relate to methods and compositions useful for routing and tracking multiple mobile units within a microfluidic device. Mobile units may be routed through a plurality of chemical environments, and the mobile units may be tracked to determine the path and/or environments that the mobile units have routed through. Mobile units may be routed in accordance with a predetermined algorithm. Mobile units may be routed through microfluidic devices in ordered flow. Mobile units routed through the microfluidic device can be used to perform various chemical reactions uniquely associated to the units, including without limitation peptide synthesis, enzymatic gene synthesis and gene assembly.