The present disclosure provides fluidic devices and fluidic device assemblies, including microfluidic devices and cartridges comprising the same, that in illustrative embodiments, can be used to make particles or protein precipitates, or to monitor precipitate formation. The fluidic devices typically include channels that connect a reaction well to an inlet port and an outlet port, and a fluidic constriction channel that is configured to help retain fluids in the reaction well and/or promote mixing within the reaction well. In some aspect, fluidic devices are interconnected into fluidic assemblies that can be used in continuous process methods.