Quorum Sensing in Emulsion Droplet Swarms Driven by a Surfactant Competition System

Area of Science:

• Chemical Engineering
• Soft Matter Physics
• Biophysics

Background:

• Quorum sensing allows unicellular organisms to coordinate behavior based on population density.
• This phenomenon is crucial for microbial community functions and survival.
• Previous systems lacked dynamic control and collective responses in engineered systems.

Purpose of the Study:

• To establish quorum sensing in artificial emulsion droplet swarms.
• To enable density-dependent collective behaviors in engineered droplet systems.
• To explore applications in sensing, optics, and controlled droplet-reactors.

Main Methods:

• Engineered oil droplets that release surfactant precursors to form imine surfactants.
• Utilized surface tension gradients and capillary attraction for droplet interaction control.
• Exploited pH-dependence of imine surfactant formation for triggered responses.
• Coupled droplet clustering to a fluorescent reporter system.

Main Results:

• Droplet swarms exhibited density-dependent clustering above a critical population density.
• Surface tension gradients and imine surfactant formation mediated repulsion and attraction.
• Spatiotemporally controlled clustering and spreading were achieved using pH stimuli.
• A fluorescent signal was generated upon clustering of specific droplet subpopulations.

Conclusions:

• Quorum sensing can be engineered in droplet-based systems for collective responses.
• This work provides a platform for dynamic control and sensing in microfluidic systems.
• Potential applications include responsive materials, optical devices, and micro-reactors.