2025 AIChE Annual Meeting

(266d) Chemical Interactions in Active Droplets

Authors

Prateek Dwivedi - Presenter, Indian Institute of Technology Kanpur
Dipin Pillai, University of Florida
Interactions among biologically active agents is facilitated by their self-generated chemical and hydrodynamic fields. In order to elucidate the pair-wise interactions between such micro-organisms, we employ active droplets as a model system, capable of self-generating chemical and hydrodynamic fields. We demonstrate that the solute Péclet number (Pe), characterizing the relative strength of its convective to diffusive transport, plays a crucial role in determining how the chemical and hydrodynamic fields impact their interactions. Our findings reveal that at low Pe, the interaction is predominantly governed by chemo-repulsive effects, leading to droplets avoiding physical contact. Conversely, at elevated Pe, hydrodynamic interactions become more influential, leading to physical engagement. However, irrespective of Pe, the interaction of a droplet with the chemical trail of another droplet is always governed by chemo-repulsive effects. Furthermore, our results establish that the chemo-repulsive deflection/rebounding of droplets is influenced by the droplets' inherent chemical polarity, as determined by its Pe, independent of their approach orientation. Our findings offer a methodology for tuning the outcomes of binary interactions among chemically active droplets, laying the groundwork for potential studies on their collective dynamics.