Gas–Liquid Microfluidics: Transition Hysteresis Behavior between Parallel Flow and Taylor Flow

Abstract

Generating gas–liquid Taylor flow is the prerequisite for the application of gas–liquid microfluidics. However, a suitable operating method for gas–liquid microfluidics has yet to be reported. Due to the different operating methods, this work finds a novel phenomenon of the strong hysteresis of the flow state transformation between parallel flow and Taylor flow in gas–liquid microfluidics. Three different flow regions are defined: parallel flow region, bistable region, and Taylor flow region. Importantly, the hysteresis phenomenon in the bistable region could be the first time reported in gas–liquid microfluidics. Results show that the flow state in the bistable region under given operating parameters strongly depends on the system’s initial state, and the hydrodynamics of parallel flow and Taylor flow under the bistable region is controlled by kinetic energy and interfacial energy, respectively. The phenomenon reminds researchers to follow a suitable operating method for gas–liquid microfluidics.