Emergence of bimodal motility in active droplets

Abstract

To explore and react to their environment, living micro-swimmers have developed sophisticated strategies for locomotion - in particular, motility with multiple gaits. To understand the physical principles associated with such a behavioural variability,synthetic model systems capable of mimicking it are needed. Here, we demonstrate bimodal gait switching in autophoretic droplet swimmers. This minimal experimental system is isotropic at rest, a symmetry that can be spontaneously broken due to the nonlinear coupling between hydrodynamic and chemical fields, inducing a variety of flow patterns that lead to different propulsive modes. We report a dynamical transition from quasi-ballistic to bimodal chaotic motion, controlled by the viscosity of the swimming medium. By simultaneous visualisation of the chemical and hydrodynamic fields, supported quantitatively by an advection-diffusion model, we show that higher hydrodynamic modes become excitable with increasing viscosity, while the recurrent mode-switching is driven by the droplet's interaction with self-generated chemical gradients. We further demonstrate that this gradient interaction results in anomalous diffusive swimming akin to self-avoiding spatial exploration strategies observed in nature.

References in corpus (24)

• Bacterial hopping and trapping in porous media
• Self-propulsion of pure water droplets by spontaneous Marangoni stress driven motion
• Chemotaxis and auto-chemotaxis of self-propelling artificial droplet swimmers
• Gravitaxis of asymmetric self-propelled colloidal particles
• Predator-Prey Interactions between Droplets Driven by Nonreciprocal Oil Exchange
• Spontaneous autophoretic motion of isotropic particles
• Anomalous Diffusion of Symmetric and Asymmetric Active Colloids
• Artificial Rheotaxis
• Bacteria display optimal transport near surfaces -- bacteria as intermittent active chiral particles: trapped by hydrodynamics, escaping by adhesion
• Oscillatory surface rheotaxis of swimming E. coli bacteria
• Vortex arrays and ciliary tangles underlie the feeding-swimming tradeoff in starfish larvae
• Cross-stream migration of active particles
• Swimming active droplet: A theoretical analysis
• Nonlinear dynamics of a chemically-active drop: from steady to chaotic self-propulsion
• Self-propulsion near the onset of Marangoni instability of deformable active droplets
• E. coli "super-contaminates" narrow ducts fostered by broad run-time distribution
• Run stop shock, run shock run: Spontaneous and stimulated gait-switching in a unicellular octoflagellate
• Exact phoretic interaction of two chemically-active particles
• Topological Stabilization and Dynamics of Self-propelling Nematic Shells
• Superwalking droplets
• Tunable active rotational diffusion in swimming droplets
• Flagellar number governs bacterial spreading and transport efficiency
• Bouncing, chasing or pausing: asymmetric collisions of active droplets
• Tunable bimodal explorations of space from memory-driven deterministic dynamics

Cited by in corpus (19)

• Chemotactic self-caging in active emulsions
• Interactions in Active Colloids
• Collective entrainment and confinement amplify transport by schooling micro-swimmers
• Solute Induced Jittery Motion of Self-Propelled Droplets
• Instability and self-propulsion of active droplets along a wall
• Instabilities driven by diffusio-phoretic flow on catalytic surfaces
• Unsteady dynamics of a classical particle-wave entity
• Confined self-propulsion of an isotropic active colloid
• Attractor-driven matter
• Interfacial activity dynamics of confined active droplets
• Self-avoidant memory effects on enhanced diffusion in a stochastic model of environmentally responsive swimming droplets
• Active particle motion in Poiseuille flow through rectangular channels
• Overload wave-memory induces amnesia of a self-propelled particle
• A Reduced Model for a Phoretic Swimmer
• Stop-and-go locomotion of superwalking droplets
• Non-Brownian diffusion and chaotic rheology of autophoretic disks
• Shapes and dynamic regimes of a polar active fluid droplet under confinement
• Steady state propulsion of isotropic active colloids along a wall
• Inverted Sedimentation of Active Particles in Unbiased ac Fields