Self-assembly and nonlinear dynamics of dimeric colloidal rotors in cholesterics

Area of Science:

• Soft Matter Physics
• Colloidal Science
• Liquid Crystal Physics

Background:

• Cholesteric liquid crystals exhibit unique director fields.
• Colloidal particles interact within complex fluid environments.
• Surface alignment of liquid crystal order parameters is crucial for particle interactions.

Purpose of the Study:

• To investigate the physics of two colloidal particles in a cholesteric liquid crystal.
• To understand the effective forces and assembly behavior of colloid dimers.
• To analyze the rotational dynamics of dimers under an applied force.

Main Methods:

• Computational simulations were employed to model the system.
• The study focused on tangential order parameter alignment at particle surfaces.
• Analysis involved tracking dimer orientation and phase lag relative to the director field.

Main Results:

• An attractive short-range effective force between colloidal particles was identified.
• Colloid dimers favor assembly at specific orientations relative to the director field.
• Dimers exhibit continuous rotation or stepwise rotation with phase-slip events when pulled along the helical axis.

Conclusions:

• A sharp dynamical transition governs the rotational behavior of colloid dimers.
• The dimer's rotation leads to either a constant or an increasing phase lag with the local nematic director.