Activity-induced instability of phonons in 1D microfluidic crystals

Area of Science:

• Physics
• Soft Matter Physics
• Fluid Dynamics

Background:

• One-dimensional crystals in microfluidic channels exhibit collective vibrational modes called phonons.
• These phonons are driven by hydrodynamic interactions and are typically neutrally stable.
• Particle activity (self-propulsion) can alter these collective behaviors.

Purpose of the Study:

• To investigate the impact of particle activity on the emergence and stability of phonons in microfluidic crystals.
• To understand how self-propulsion influences wave propagation direction and introduces new instabilities.
• To explore the phenomenon of phonon switching between adjacent crystal structures.

Main Methods:

• Analysis of collective vibrational modes in one-dimensional particle crystals.
• Theoretical investigation of hydrodynamic interactions and particle activity.
• Simulation or experimental observation of wave propagation and stability in microfluidic systems.

Main Results:

• Wave propagation direction in active crystals depends on background flow intensity.
• Particle activity induces a new instability by coupling transverse waves to rotational motion.
• Phonon switching between adjacent crystals observed in both passive and active systems.

Conclusions:

• Particle activity significantly modifies phonon dynamics in microfluidic systems.
• The identified instability and phonon switching phenomena offer new insights into active matter behavior.
• Findings have potential applications in designing microfluidic devices and controlling micro-particle self-assembly.