Pure Hydrodynamic Instabilities in Active Jets of Puller Microalgae.

Area of Science:

• Physics of active matter
• Microbiology
• Fluid dynamics

Background:

• Active fluids exhibit spontaneous flow instabilities and complex patterns.
• Controlling active particles spatiotemporally is challenging but crucial for biological and applied fields.

Purpose of the Study:

• To demonstrate spatiotemporal control of active particles using phototaxis.
• To investigate the control of flow instabilities in active fluids.

Main Methods:

• Utilized phototaxis to steer millions of swimming Chlamydomonas reinhardtii algae.
• Employed preferential cell orientation to control active jets and instabilities.
• Combined experimental data with analytical modeling and simulations.

Main Results:

• Successfully created active jets and controlled pearling and buckling instabilities.
• Confirmed theoretical predictions of self-generated flow leading to jet destabilization.
• Showed that 'puller' algae can mimic 'pusher' behavior with proper orientation tuning.

Conclusions:

• Light-enabled phototaxis provides efficient control over active fluids.
• Demonstrated a novel method for manipulating active particle behavior and instabilities.
• Opened new avenues for applications requiring precise control of microscale active systems.