Tunable structure and dynamics of active liquid crystals.

Area of Science:

• Soft Matter Physics
• Non-equilibrium Systems
• Active Matter

Background:

• Active materials convert free energy into directed motion, exhibiting complex dynamical phenomena.
• Understanding the structure-dynamics relationship in active materials is crucial for controlling their behavior and enabling applications.
• Active nematics, composed of filaments and motors, represent a model system for studying non-equilibrium physics.

Purpose of the Study:

• To investigate the non-equilibrium properties of active nematics across varying internal activity levels.
• To understand how topological defect interactions and system elasticity are influenced by activity.
• To explore the potential for designing active materials with engineered dynamic responses.

Main Methods:

• Concerted theoretical and experimental strategy applied to a quasi-two-dimensional sheet of actin filaments driven by myosin II motors.
• Analysis of topological defect interactions as a function of initial separation and relative orientation.
• Examination of +1/2 defect morphology and apparent elastic properties (bend-to-splay modulus ratio) at different activity levels.

Main Results:

• Topological defect interactions transition from attractive to repulsive based on separation and orientation.
• Increased activity significantly alters apparent elastic properties, reducing effective bend elasticity.
• At high activity, topological defects exhibit liquid-like structures and preferred orientations based on topological charge.

Conclusions:

• The study provides new insights into the non-equilibrium physics of active nematics.
• Tunable internal stresses are achievable by controlling activity levels.
• These findings pave the way for designing out-of-equilibrium structures with engineered dynamic responses.