Dynamics of an active Belousov-Zhabotinsky droplet in shear flow

Abstract

Navigation of self-propelled active particles in complex biological environments has been a grand challenge for researchers for the past few decades. Here, we design a self-driven synthetic active droplet system, based on self-oscillating Belousov-Zhabotinsky (BZ) reaction, and investigate droplet dynamics in a confined shear flow. Our approach harnesses two phase multicomponent lattice Boltzmann method, in conjunction with phase-field model, to capture the dynamics of active droplet immersed in a flowing liquid. We demonstrate that this background flow of the fluid breaks the symmetry and produces concentration nucleation spots in the BZ droplet, propelling the droplet by Marangoni effect. The specific locations of these spots and the droplet's trajectory is governed by reaction kinetics, droplet deformation, type of surfactant and the flow of the surrounding fluid. Thus, unlike a passive droplet in a shear flow, our active BZ droplet exhibits self-propelled motion that can be directed in both lateral and longitudinal directions, by the velocity of the surrounding fluid. In summary, our study unveils the fascinating interplay of background flow and self-propulsion and thus, unfolds the underlying mechanism for the directional motion of an active BZ droplets. Our findings can be used to design active droplet-based systems that mimic the functionalities of complex biological systems and opens up promising avenues for various microfluidic, therapeutic, drug delivery applications, to name a few.