Self-assembly of colloidal micelles in microfluidic channels

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Computational Fluid Dynamics

Background:

• Amphiphilic Janus colloids exhibit self-assembly behavior driven by solvophobic interactions.
• Microfluidic channels provide a confined environment influencing colloidal self-assembly dynamics.
• Hydrodynamic interactions play a crucial role in the behavior of colloidal suspensions.

Purpose of the Study:

• To investigate the self-assembly of Janus colloids in microfluidic channels.
• To understand the impact of Poiseuille flow on colloidal micelle formation and stability.
• To explore the role of channel wall interactions in confined colloidal systems.

Main Methods:

• Hybrid molecular dynamics simulations were employed.
• Fully resolved hydrodynamic interactions were incorporated using the multi-particle collision dynamics (MPCD) algorithm.
• Simulations were conducted under varying Poiseuille flow conditions within a microfluidic channel.

Main Results:

• Janus particles spontaneously self-assembled into spherical micelles to minimize solvophobic surface area.
• Channel wall material influenced particle aggregation, with solvophobic walls attracting free particles and small clusters.
• Flow dynamics induced micelle breakup at high rates, but intermediate rates led to micelle growth and the formation of 13-particle icosahedral clusters.
• A non-uniform cluster size distribution was observed, with aggregation numbers decreasing near the channel walls due to the parabolic velocity profile.

Conclusions:

• The study elucidates the complex interplay between Janus colloid self-assembly, microfluidic confinement, and shear flow.
• Flow rate is a critical parameter controlling micelle stability, breakup, and growth dynamics.
• Channel wall properties significantly affect particle distribution and aggregation behavior in confined systems.