The role of reactant contact modes in droplet-based microfluidics

Abstract

Undesired side reactions can significantly impact the efficiency and economic viability of chemical processes. Droplet-based microfluidics(DBM) offers precise control over reaction conditions by isolating reactants in distinct droplets. Each droplet acts as microreactor with high surface-to-volume ratio. This paper comprehensively investigates the role of two reactant contact modes that give rise to droplet flow. The first contact-mode, Conjugate Mass Transfer Mode(CMTM), is characterized by mass transfer of a reactant from Continuous phase(CP) to Dispersed phase(DP). In second mode, Single-Sphere Mode(SSM), both reactants coexist within the dispersed phase, and there is no effect of external mass transfer on performance. The Hadamard-Rybczynski flow field is used to obtain insights into the system behavior. Two reaction networks, Parallel and Series-Parallel reactions, are considered, which arise from side reactions that accompany the primary reaction.This work highlights the importance of choosing an appropriate reactant contact-mode when side reactions occur. The role of two experimentally controllable parameters, diffusivity ratio(Dr) and feed concentration ratio(M), is analyzed to identify the desirable contact mode. Notably, our study showed that, for Parallel reactions, CMTM has a superior performance compared to SSM under some conditions. Whereas for Series-Parallel reactions, SSM exhibits better performance when equal concentrations of reactants are employed.