Excitability induced binary interactions in self-propelled Belousov-Zhabotinsky droplets

Area of Science:

• Chemical kinetics
• Nonlinear dynamics
• Active matter physics

Background:

• The Belousov-Zhabotinsky (BZ) reaction is a classic example of a nonlinear chemical oscillator.
• Self-propelled motion of BZ droplets in oil is driven by internal chemical oscillations and the boundary Marangoni effect.

Purpose of the Study:

• To investigate how excitability, specifically sodium bromate concentration, influences the behavior and interactions of BZ droplets.
• To analyze the impact of varying droplet volumes on their interaction dynamics.

Main Methods:

• Experimental manipulation of sodium bromate concentration in BZ reaction droplets.
• Observation and analysis of individual droplet motion (oscillation frequency, speed, direction).
• Study of interactions between single and multiple BZ droplets, including varying volumes.

Main Results:

• Increased sodium bromate concentration leads to higher oscillation frequency, faster droplet speed, and more frequent direction changes.
• Higher sodium bromate concentrations decrease the interaction time between multiple BZ droplets.
• Observed three interaction patterns for droplets of different volumes: head-on approach, parallel paths, and larger droplet following smaller droplet.
• Maximum interaction time occurred when a larger droplet followed a smaller one.

Conclusions:

• Sodium bromate concentration is a key factor in controlling BZ droplet dynamics and interactions.
• Understanding these interactions provides insights into emergent phenomena in active matter systems.
• The observed behaviors offer potential for controlling active matter systems through chemical means.